· Web viewP3 10 Motor Effect Exam Questions 154 minutes 154 marks Q1. Circuit breakers help to...

P3 10 Motor Effect Exam Questions

154 minutes

154 marks

Q1. Circuit breakers help to make the electricity supply in homes safer.A circuit breaker is an automatic safety switch. It cuts off the current if it gets too big.

Describe, in as much detail as you can, how this circuit breaker works.

To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(Total 6 marks)

Q2. A fault in an electrical circuit can cause too great a current to flow.Some circuits are switched off by a circuit breaker.

One type of circuit breaker is shown above. A normal current is flowing.Explain, in full detail, what happens when a current which is bigger than normal flows.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(Total 4 marks)

Q3. The diagram below shows a door lock which can be opened from a flat inside a building.

(a) Explain how the door is unlocked when the switch is closed.

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................

....................................................................................................................................(4)

(b) State two changes which would increase the strength of the electromagnet.

1 ..................................................................................................................................

2 ..................................................................................................................................(2)

(c) Why is the spring needed in the lock?

....................................................................................................................................

....................................................................................................................................(1)

(d) The connections to the coil were accidentally reversed. Would the lock still work?

....................................................................................................................................

Explain your answer.

....................................................................................................................................

....................................................................................................................................(2)

(Total 9 marks)

Q4. The diagram shows apparatus used to demonstrate the motor effect. X is a short length of bare copper wire resting on two other wires.

(a) (i) Describe what happens to wire X when the current is switched on.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

(ii) What difference do you notice if the following changes are made?

A The magnetic field is reversed.

...........................................................................................................................

...........................................................................................................................

B The current is increased.

...........................................................................................................................

...........................................................................................................................(3)

(b) The diagram shows a coil placed between the poles of a magnet. The arrows on the sides of the coil itself show the direction of the conventional current.

The arrows labelled F show the direction of the forces acting on the sides of the coil. Describe the motion of the coil until it comes to rest.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(c) Most electric motors use electromagnets instead of permanent magnets. State three of the features of an electromagnet which control the strength of the magnetic field obtained.

1 ................................................................................................................................

2 ................................................................................................................................

3 ................................................................................................................................(3)

(Total 9 marks)

Q5. The diagram shows a switch that is operated by an electromagnet.

(i) What is this type of switch called?

.....................................................................................................................................(1)

(ii) The switch is used in a car starter motor circuit.

Explain how turning the ignition key makes a current flow in the starter motor. The explanation has been started for you.

When the ignition key is turned ..................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(Total 4 marks)

Q6. The diagram shows apparatus used to demonstrate the electric motor effect. When he switch is closed the wire moves.

(i) Draw an arrow on the diagram to show the direction the wire moves.(1)

(ii) Explain why the wire moves.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 3 marks)

Q7. (a) Name a material that could be used to make the outside case of the plug.

.....................................................................................................................................

Give a reason for your choice.

.....................................................................................................................................

.....................................................................................................................................(2)

(b) To gain full marks in this question you should write your ideas in good English. Put them into a sensible order and use the correct scientific words.

Some electrical circuits are protected by a circuit breaker. These switch the circuit off if a fault causes a larger than normal current to flow. The diagram shows one type of circuit breaker. A normal current (15 A) is flowing.

Source: adapted from V. PRUDEN and K. HIRST, AQA GCSE SceinceReproduced by permission of Hodder and Soughton Educational Ltd

Explain what happens when a current larger than 15A flows. The answer has been started for you.

When the current goes above 15 A, the electromagnet becomes stronger and

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(Total 5 marks)

Q8. The diagram shows the design for a remotely controlled door bolt.

When the correct numbers are entered into the keypad the transformer switches on. Then the door can be opened.

(a) What kind of transformer is shown in the diagram?

....................................................................................................................................(1)

(b) What does the abbreviation a.c. stand for?

....................................................................................................................................(1)

(c) Complete the sentences using the correct words from the box.

attracts downwards magnet reflects repels

sideways switch transformer upwards

(i) When a current flows in the coil, the coil becomes a ................................... .

(ii) The coil ................................... the iron bolt which moves ............................(3)

(Total 5 marks)

Q9. When a conductor carrying an electric current is placed in a magnetic field a force may act on it.

(a) State two ways in which this force can be increased.

1 ..................................................................................................................................

2 ..................................................................................................................................(2)

(b) State two ways in which this force can be made to act in the opposite direction.

1 ..................................................................................................................................

2 ..................................................................................................................................(2)

(c) In what circumstance will no force act on a conductor carrying an electric current and in a magnetic field?

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 5 marks)

Show clearly how you work out your answer.

.....................................................................................................................................

.....................................................................................................................................

Kinetic energy = ............................................... J(2)

(Total 7 marks)

Q10. Many electrical appliances use the circular motion produced by their electric motor.

(a) Put ticks ( ) in the boxes next to all the appliances in the list which have an electric motor.

electric drill

electric fan

electric food mixer

electric iron

electric kettle

electric screwdriver

(2)

(b) One simple design of an electric motor is shown in the diagram. It has a coil which spins between the ends of a magnet.

(i) Give two ways of reversing the direction of the forces on the coil in the electric motor.

1 ........................................................................................................................

...........................................................................................................................

2 ........................................................................................................................

...........................................................................................................................(2)

(ii) Give two ways of increasing the forces on the coil in the electric motor.

1 ........................................................................................................................

...........................................................................................................................

2 ........................................................................................................................

...........................................................................................................................(2)

(Total 6 marks)

Q11.A student used the apparatus shown in the diagram to investigate how the weight supported by an electromagnet depends on:

• the current, I, flowing through the wire

• the number of turns of wire, n, wrapped around the iron core.

For different values of I and n the student measured the maximum weight supported by the electromagnet.

(a) Which one of the following is the circuit symbol for a variable resistor?

Draw a ring around one answer.

(1)

(b) The student obtained the three sets of results given below.

I = 2.5 A I = 1.0 A I = 2.0 A n = 20 n = 30 n = 10 W = 6.4 N W = 6.5 N W = 3.7 N

Considering only these results, explain why it is not possible to come to any conclusion about how I and n separately affect the strength of the electromagnet.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(c) The student obtained more results, and plotted the graph shown below.

Analyse all the results on the graph to draw conclusions for this investigation.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(5)

(d) The greater the weight supported, the stronger the electromagnet.

The smallest current that gives an electromagnet maximum strength is called thesaturation current.

What is the saturation current for the electromagnet with 30 turns of wire?

.....................................................(1)

(e) The diagram shows the circuit for the electric starter motor of a car. The circuit includes a relay switch, which is a switch closed by an electromagnet.

(i) Explain how turning the ignition key causes the starter motor to work.

The explanation has been started for you.

When the ignition key is turned the switch S closes and ...

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(4)

(ii) Electric starter motors are always less than 100% efficient.

Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................(3)

(Total 16 marks)

Q12. In this question you will be assessed on using good English, organising information clearlyand using specialist terms where appropriate.

The diagrams show a relay switch and how it is used in a car ignition circuit.

Turning the ignition key closes the ignition switch.Explain how this causes the starter motor to operate.

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................(Total 6 marks)

Q13. The diagram shows the equipment used by a student to investigate the strength of five different electromagnets.

The stronger the electromagnet, the more paper clips it will hold.

(a) Why is it important that the paper clips used in the investigation are all the same size?

........................................................................................................................

........................................................................................................................

........................................................................................................................(1)

(b) The five electromagnets, J, K, L, M and N, used by the student are shown below.Each electromagnet was made by wrapping lengths of insulated wire around identical iron nails.

The student wants to find out how the strength of an electromagnet depends on the number of turns of wire in the coil.

Which electromagnets should the student compare in order to do this?

........................................................................................................................(1)

(c) The student concluded:

“The strength of an electromagnet is always directly proportional to the number of turns on the coil.”

(i) Explain how the data from the investigation supports the student’s conclusion.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(ii) The student makes one more electromagnet by winding 100 turns onto a nail.

Before testing the electromagnet, the student predicted the number of paper clips that the electromagnet would hold when the current is 1 amp.

How many paper clips should the student predict that the electromagnet would hold?


...............................................................................................................

...............................................................................................................

...............................................................................................................

number of paper clips = .....................................(2)

(iii) When the student tested the electromagnet it held 20 paper clips.This is not what the student predicted.

Explain what the student should do when new data does not seem to support the prediction that was made.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(3)

(Total 9 marks)

Q14. (a) A laboratory technician sets up a demonstration.

A flexible wire is suspended between the ends of a horseshoe magnet. The flexible wire hangs from a cotton thread. When the switch is closed, the wire kicks forward.

Identify the effect which is being demonstrated.

........................................................................................................................(1)

(b) A teacher makes some changes to the set-up of the demonstration.

What effect, if any, will each of the following changes have?

(i) more powerful horseshoe magnet is used.

...............................................................................................................

...............................................................................................................(1)

(ii) The connections to the power supply are reversed.

...............................................................................................................

...............................................................................................................(1)

(Total 3 marks)

Q15. A student investigates the electromagnetic force acting on a wire which carries an electric current. The wire is in a magnetic field.

The diagram shows the circuit which the student uses.

(a) Draw an X on the diagram, with the centre of the X in the most strongest part of the magnetic field.

(1)

(b) Give one change that she can make to the magnets to decrease the electromagnetic force on the wire.

........................................................................................................................

........................................................................................................................(1)

(c) The student wants to change the electromagnetic force on the wire without changing the magnets or moving their position.

(i) Give one way in which she can increase the electromagnetic force.

...............................................................................................................

...............................................................................................................(1)

(ii) Give one way in which she can reverse the direction of the electromagnetic force.

...............................................................................................................

...............................................................................................................(1)

(Total 4 marks)

Q16. (a) A science technician sets up the apparatus shown below to demonstrate the motor effect. He uses a powerful permanent magnet.

The copper roller is placed across the metal rails. When the switch is closed, the copper roller moves to the right.

(i) Complete the sentence by drawing a ring around the correct line in the box.

an electrical conductor.

This happens because copper is an electrical insulator.

a magnetic material.

(1)

(ii) Suggest one change that the technician can make which will cause the copper roller to move faster.

...............................................................................................................

...............................................................................................................(1)

(iii) Suggest two changes which the technician can make, each of which will separately cause the copper roller to move to the left.

1 ............................................................................................................

...............................................................................................................

2 ............................................................................................................

...............................................................................................................

(2)

(b) Many electrical appliances, such as vacuum cleaners, drills and CD players, contain electric motors. As more electrical appliances are developed, more electricity needs to be generated. Generating electricity often produces pollutant gases.

(i) Complete the sentence by drawing a ring around the correct line in the box.

Generating more electricity to power the increasing number of electrical appliances used

an ethical

raises

an environmental issue.

a political

(1)

(ii) The number of electrical appliances used in the world’s richest countries is increasing yet many people in the world’s poorest countries have no access to electricity.

What type of issue does this inequality between people in different countries raise?

...............................................................................................................(1)

(Total 6 marks)

Q17. (a) Complete the description of the device shown below by drawing a ring around the correct line in each box.

an electric motor.

(i)

The device is being used as a generator.

a transformer.

(1)

(ii) The coil needs a flick to get started. Then one side of the coil is pushed by the

cell

coil and the other side is pulled, so that the coil spins.

force

(1)

(b) Suggest two changes to the device, each one of which would make the coil spin faster.

1 ......................................................................................................................

........................................................................................................................

2 ......................................................................................................................

........................................................................................................................(2)

(c) Suggest two changes to the device, each one of which would make the coil spin in the opposite direction.

1 ......................................................................................................................

........................................................................................................................

2 ......................................................................................................................

........................................................................................................................(2)

(Total 6 marks)

Q18.The diagram shows a device called a current balance.

(a) (i) When the switch is closed, the part of the wire labelled XY moves upwards.

Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(ii) What is the name of the effect that causes the wire XY to move?

...............................................................................................................(1)

(iii) An alternating current (a.c.) is a current which reverses direction. How many times the current reverses direction in one second depends on the frequency of the alternating supply.

Describe the effect on the wire XY if the battery is replaced by an a.c. supply having a frequency of 5 hertz.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(b) The diagram shows how a small weight can be used to make the wire XY balance horizontally.

Use the data in the diagram and the equation in the box to calculate the force, F, acting on the wire XY.

moment = force × perpendicular distance from the line ofaction of the force to the axis of rotation


........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Force = ............................................................ N(3)

(Total 8 marks)

Q19.The diagram shows a student’s design for a simple wind speed gauge.

(a) Explain why the wind causes the a.c. voltmeter to give a reading. The explanation has been started for you.

The wind causes the plastic cups to turn. .....................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(b) The gauge is not sensitive enough to measure light winds.

Suggest one way that the design can be modified to make the gauge more sensitive.

........................................................................................................................

........................................................................................................................(1)

(Total 4 marks)

Q20.A student has made a simple electric motor. The diagram shows the electric motor.

(a) Complete the following sentence by drawing a ring around the correct line in the box.

the cell

Once the coil is spinning, one side of the coil is pushed by the coil and the other

a force

side is pulled, so the coil continues to spin.(1)

(b) Suggest two changes to the electric motor, each one of which would make the coil spin faster.

1 .....................................................................................................................

........................................................................................................................

2 .....................................................................................................................

........................................................................................................................(2)

(c) Suggest two changes to the electric motor, each one of which would make the coil spin in the opposite direction.

1 ........................................................................................................................

........................................................................................................................

2 ........................................................................................................................

........................................................................................................................(2)

(Total 5 marks)

Q21.The diagram shows a ‘G-machine’. The G-machine is used in astronaut training.

The G-machine moves the astronaut in a horizontal circle.

(a) When the G-machine is rotating at constant speed, the astronaut is accelerating.

State the name and direction of the force causing the astronaut to accelerate.

Name of force ................................................................................................

Direction of force ...........................................................................................

........................................................................................................................(2)

(b) The force causing the astronaut to move in a circle is measured.

The graph shows how the speed of the astronaut affects the force causing the astronaut to move in a circle for two different G-machines.

The radius of rotation of the astronaut is different for each G-machine.

Speed in metres per second

(i) State three conclusions that can be made from the graph.

1 ............................................................................................................

...............................................................................................................

2 ............................................................................................................

...............................................................................................................

3 .............................................................................................................

...............................................................................................................(3)

(ii) The speed of rotation of G-machine 1 is increased from 20 m/s to 40 m/s.

Determine the change in force on the astronaut.

...............................................................................................................

Change in force = ............................................................ N(1)

(c) Each G-machine is rotated by an electric motor. The diagram shows a simple electric motor.

(i) A current flows through the coil of the motor.

Explain why side A of the coil experiences a force.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(ii) Draw arrows on the diagram to show the direction of the forces acting on side A of the coil and side C of the coil.

(1)

(iii) When horizontal, side B experiences no force.

Give the reason why.

...............................................................................................................

...............................................................................................................(1)

(d) While a G-machine is rotating, the operators want to increase its speed.

What can the operators do to make the G-machine rotate faster?

........................................................................................................................

........................................................................................................................(1)

(e) The exploration of space has cost a lot of money.

Do you think spending lots of money on space exploration has been a good thing?

Draw a ring around your answer.

Yes No

Give a reason for your answer.

........................................................................................................................

........................................................................................................................(1)

(Total 12 marks)

Q22.The diagram shows a ‘G-machine’. The G-machine is used in astronaut training.

The G-machine moves the astronaut in a horizontal circle.

(a) In which direction, A, B or C, does the centripetal force on the astronaut act?

Write your answer in the box.

(1)

(b) The centripetal force on the astronaut is measured.

Graph X shows how the centripetal force is affected by the speed of rotation.The radius of rotation is kept the same.

Speed of rotationin metres per second

(i) Use Graph X to determine the centripetal force on the astronaut when rotating at a speed of 30 metres per second.

Centripetal force = .............................. newtons(1)

(ii) Complete the following sentence to give the conclusion that can be made fromGraph X.

Increasing the speed of rotation of a G-machine will ................................................

the centripetal force on the astronaut.(1)

(iii) Graph Y shows how the centripetal force is affected by the radius of rotation, when the speed of rotation is kept the same.

Radius of rotationin metres

Complete the following sentence to give the conclusion that can be made fromGraph Y.

The greater the radius of rotation, the ......................................... the centripetal force

on the astronaut.(1)

(c) The G-machine is rotated by an electric motor. The diagram shows a simple electric motor.

The following statements explain how the motor creates a turning force. The statements are in the wrong order.

M – The magnetic field interacts with the magnetic field of the permanent magnets.

N – A magnetic field is created around the coil.

O – The power supply applies a potential difference across the coil.

P – This creates a force that makes the coil spin.

Q – A current flows through the coil.

Arrange the statements in the correct order. Two of them have been done for you.

(2)

(d) The electric motor produces a turning force.

Give two ways of increasing the turning force.

1 .....................................................................................................................

........................................................................................................................

2 .....................................................................................................................

........................................................................................................................(2)

(e) Draw a ring around the correct answer to complete the sentence.

It costs a lot of money to send astronauts into space.

an economic

This is an environmental issue.

a social

(1)(Total 9 marks)

Q23.(a) Some people wear magnetic bracelets to relieve pain.

Figure 1 shows a magnetic bracelet.

There are magnetic poles at both A and B.Part of the magnetic field pattern between A and B is shown.

Figure 1

What is the pole at A? ...........................................

What is the pole at B? ...........................................(1)

(b) Figure 2 shows two of the lines of the magnetic field pattern of a current-carrying wire.

Figure 2

The direction of the current is reversed.

What happens to the direction of the lines in the magnetic field pattern?

.........................................................................................................................(1)

(c) Fleming’s left-hand rule can be used to identify the direction of a force acting on a current-carrying wire in a magnetic field.

(i) Complete the labels in Figure 3.

Figure 3

(2)

(ii) Figure 4 shows:

• the direction of the magnetic field between a pair of magnets

• the direction of the current in a wire in the magnetic field.

Figure 4

In which direction does the force on the wire act?

................................................................................................................(1)

(iii) Suggest three changes that would decrease the force acting on the wire.

1 ..........................................................................................................

2 ..........................................................................................................

3 ..........................................................................................................

(3)

(d) Figure 5 shows part of a moving-coil ammeter as drawn by a student.

The ammeter consists of a coil placed in a uniform magnetic field.When there is a current in the coil, the force acting on the coil causes the coil to rotate and the pointer moves across the scale.

Figure 5

(i) The equipment has not been set up correctly.

What change would make it work?

................................................................................................................

................................................................................................................(1)

(ii) Figure 6 shows the pointer in an ammeter when there is no current.

Figure 6

What type of error does the ammeter have?

................................................................................................................(1)

(Total 10 marks)

M1. Quality of written communication: One mark for correct sequencing.bolt out plunger up switch off / circuit broken

1

any five from

• high current flows

• electromagnet is stronger

• the iron bolt is pulled out

• the plastic plunger moves up

• the switch is lifted / open / offaccept circuit is broken

• no current flowing

• to re-set the plunger must be pushed down5

[6]

M2. electromagnet becomes stronger (not becomes magnetic) iron moves left – implied OKplunger goes up push switch goes to off or circuit broken unless plunger moves down

for 1 mark each[4]

M3. (a) current flowscoil / core magnetised / electromagnet activated / energised / turned onattracts iron bar causing bolt to be pulled out

each for 1 mark4

(b) more turnsbigger current / e.m.fsofter iron core

any two for 1 mark each2

(c) to relock door / return iron bar / to lock doorfor 1 mark

1

(d) iron bar would still be attracted / coil still magnetised so still worksfor 1 mark each

yes + wrong answer0 marks

yes + current still flows1 mark

yes + still magnetised / iron bar still attracted2 marks

2[9]

M4. (a) (i) it moves or experiences a force horizontally to the rightfor 1 mark

1

(ii) A – moves in opposite direction or force reversed e.c.f. B – faster movement or larger force(not move further)

for 1 mark each2

(b) turns clockwiseoscillates/reversescomes to rest facing field/at 90o to field/vertically

for 1 mark each3

(c) number of turns or linear number density of turns current corefor 1 mark each

3[9]

M5. (i) relayaccept solenoiddo not accept magnetic switch

1

(ii) a current flows through the coil (of the electromagnet)or a current flows through the electromagnetor a (magnetic) field is produced

accept ‘electricity’ for ‘current’accept the electromagnet is activated or magnetised or turned ondo not accept answer in terms of magnetic charge

1

the (iron) arm is attracted to the electromagnetaccept the arm pivots or moves towards the electromagnet

1

the contacts are pushed togetherdo not accept contacts attract

1[4]

M6. (i) away from magnetarrow should be perpendicular to field lines and current as judged by eye

1

(ii) current in wire creates magnetic field around wire1

two fields interact or combine giving a resultant force (on the wire)1

[3]

M7. (a) plastic or rubberaccept any named plasticdo not accept wood

1

it is a (good) insulator or it is a poor conductorignore mention of heat if in conjunction with electricity

1

(b) The answer to this question requires ideas in good English in asensible order with correct use of scientific terms. Quality of writtencommunication should be considered in crediting points in the mark scheme.

Maximum of 2 marks if ideas not well expressed.

pulls iron bolt down or attracts the iron bolt or moves bolt out of plungeranswers in terms of charges attractingor repelling gain no credit

1

plunger pushed / moved to the right (by spring) or plunger released1

push switch opens / goes to off / goes to rightaccept circuit is brokenfor maximum credit the points must follow a logical sequence3 correct points but incorrect sequence scores 2 marks onlyignore reset action

1[5]

M8. (a) step-down (transformer)1

(b) alternating currentaccept minor misspellings butdo not credit ‘alternative current’

1

(c) (i)(ii) magnet

attracts

upwardscorrect order essentialaccept ‘up’

3[5]

M9. (a) increase the current (1)credit increase the p.d./voltagecredit reduce the resistancecredit have thicker wiringcredit add extra / more cells

1

increase the magnetic field (strength) (1)credit ‘have stronger magnet(s)do not credit ‘bigger magnets’ either order

1

(b) either reverse polarity

or connect the battery the other way round1

either reverse direction of the magnetic field

or put the magnet the other way round / reverse the magnetdo not give any credit to a response in which both are done at the same timeeither order

1

(c) either

conductor parallel to the magnetic field

or lines of magnetic force and path of electricity do not cross1

[5]

M10. (a) electric drill, electric fan, electric food mixer and electric screwdriverall four ticked and no others (2)either all four of these ticked and only one other (1)or any three of these ticked and none/one/two of the others (1)

2

(b) (i) reverse (the direction of the) current (1)or reverse the connections (to the battery)

reverse (the direction of the) magnetic field (1)or reverse the (magnetic) poles /endsdo not credit ‘swap the magnets (around)’

2

(ii) any two from:

• increase the strength of the magnet(s)/(magnetic) fielddo not credit ‘use a bigger magnet’

• increase the currentallow ‘increase the voltage/p.d.’allow add cells/batteriesallow increase the (electrical) energyallow increase the power supplyallow ‘decrease the resistance’allow ‘increase charge’allow ‘ increase the electricity’do not credit ‘use a bigger battery’

• reduce the gap (between coil/armatureand poles/magnets)allow increase the (number of) coils

• increase the turns (on the coil/armature)do not credit ‘use a bigger coil’

2[6]

M11.(a) correct symbol identified

1

(b) because both I and n are changing1

it could be either I or n that affect Worit could be both I and n that affect W

if no other marks awarded allow 1 mark for one needs to be controlledormust only have one independent variable

1

(c) for all values of n weight supported increases with increasing currentaccept for 1 mark, weight supported increases with increasing current

2

but not linearly1

for a given current the weight supported increases with increase in n1

weight supported reaches a maximum with n = 30 turns1

(d) 2.3 (A)accept any value between 2.3 and 2.4

1

(e) (i) there is a current in the electromagnetaccept electromagnet is switched on

1

the electromagnet attracts the iron arm1

the arm pivots and pushes the contacts togetheraccept closes the switch

1

resulting in a current in the (starter) motor circuit1

(ii) electrical energy is supplied to the motor, and not all of this energy is usefully transferred to kinetic energy

1

some of the energy is wasted as thermal energy, (and sound energy)1

therefore (useful energy out divided by / total energy in) is less than 100%1

[16]

M12. Marks awarded for this answer will be determined by the Quality of WrittenCommunication (QWC) as well as the standard of the scientific response.

No relevant content.0 marks

There is a brief explanation of how a current is caused to flow in the starter motor circuit.

Level 1 (1–2 marks)

There is some explanation of how a current is caused to flow in the starter motor circuit.


There is a clear and detailed explanation of how a current is caused to flow in the starter motor circuit.


examples of the physics points made in the response

current flows through the coil / electromagnet

magnetic field producedaccept electromagnet switches on

(short side of) iron bar attracted to electromagnet

contacts pushed together (by iron bar)

starter motor circuit completed

current flows through starter motor

or

p.d. across starter motor[6]

M13. (a) so the results can be compared fairlyfair test is insufficient

1

(b) J L Mall 3 required and no other

1

(c) (i) for a given current the number of paper clips increasesby the same factor as the number of turns

1

plus a mathematical explanation using the dataeg a current of 1 A with 10 turns picks up 3 clips, acurrent of 1 A with 20 turns picks up 6 clips

1

(ii) 30allow 1 mark for showing correct use of figures eg20 turns × 5 = 100 turns

2

(iii) check the new data / repeat the experiment1

to identify any anomalous results1

then reconsider prediction / hypothesis in thelight of new evidence1

[9]

M14. (a) motor (effect)1

(b) (i) wire kicks further (forward)accept moves for kicksaccept moves moreaccept ‘force (on the wire) increased’

1

(ii) wire kicks back(wards) / into (the space in) the (horseshoe) magnetaccept moves for kicksaccept ‘direction of force reversed’

1[3]

M15. (a) centre of the X midway between the polesintention correct as judged by eyeexample

1

(b) move the poles further apartaccept turn for moveaccept ends / magnets for polesaccept use weaker magnetsdo not accept use smaller magnets

1

(c) (i) add more cells (to the battery)do not accept ‘use a bigger battery’accept increase the potential difference / voltageaccept increase the current

orreduce the resistance (of the variable resistor)

do not accept any changes to the magnets, to the wire or to their relative positions

1

(ii) reverse (the polarity of) the batteryaccept turn the battery / cells roundaccept swap the connections to the batterydo not accept any changes to the magnets, to the wire or to their

relative positions1

[4]

M16. (a) (i) an electrical conductor1

(ii) increase currentaccept increase p.d. / voltage

oruse stronger magnets

accept move magnets closerdo not accept use larger magnets

1

(iii) reverse the poles / ends (of the magnet)either order

1

reverse the connections (to the power supply)1

(b) (i) environmental1

(ii) ethicalallow political (instability)allow economic (migration)

1[6]

M17. (a) (i) an electric motor1

(ii) force1

(b) any two from:

• more powerful magnetdo not allow ‘bigger magnet’

• reduce the gap (between magnet and coil)

• increase the area of the coil

• more powerful celldo not allow ‘bigger cell’accept battery for cellaccept add a cellaccept increase current / potential difference

• more turns (on the coil)allow ‘more coils on the coil’do not allow ‘bigger coil’

2

(c) reverse the (polarity) of the cellallow ‘turn the cell the other way round’accept battery for cell

1

reverse the (polarity) of the magnetallow ‘turn the magnet the other way up’

1[6]

M18. (a) (i) current produces a magnetic field (around XY)accept current (in XY) is perpendicular to the (permanent) magnetic field

1

(creating) a force (acting) on XY / wire / upwardsreference to Fleming's left hand rule is insufficient

1

(ii) motor (effect)1

(iii) vibrate / move up and down1

5 times a secondonly scores if first mark point scoresallow for 1 mark only an answer ‘changes direction 5 times a second’

1

(b) 0.005allow 1 mark for calculating moment of the weight as 0.04 (Ncm)andallow 1 mark for correctly stating principle of momentsor

allow 2 marks for correct substitutionie F × 8 = 2 × 0.02 or F × 8 = 0.04

3[8]

M19.(a) which causes the magnet to turn / spin / rotate1

(magnetic) field / lines of force / flux rotate(s) / move(s) / through / in / cut(s) the coildo not credit the idea that movement ‘creates’ the magnetic field

1

potential difference / p.d. / voltage induced across the coildo not credit just ‘current induced’

1

(b) any one from:

• more powerful / stronger / lighter magnetdo not credit ‘a bigger magnet’

• larger / more / bigger / lighter cups / with a bigger surface area

• longer arms

• lubricate the spindle

• add more turns to the coil1

[4]

M20.(a) a force1

(b) any two from:

• more powerful magnetdo not allow ‘bigger magnet’

• reduce the gap (between magnet and coil)

• increase the area of the coil

• more powerful celldo not allow ‘bigger cell’accept battery for cellaccept add a cellaccept increase current / potential difference

• more turns (on the coil)allow ‘more coils on the coil’do not allow ‘bigger coil’

2

(c) reverse the (polarity) of the cellallow ‘turn the cell the other way round’accept battery for cell

1

reverse the (polarity) of the magnetallow ‘turn the magnet the other way up’

1[5]

M21.(a) centripetal (force)allow tension (between astronaut and seatbelt)

1

towards the centre (of the G-machine / circle)do not accept towards the centre of the Earthallow inwards

1

(b) (i) the greater the speed (of a centrifuge), the greater the forceanswers must be comparativeaccept velocity for speedaccept positive correlation between speed and forcespeed and force are not proportional – treat as neutral

1

the smaller the radius, the greater the force (at a given speed)allow (G machine) 1 has / produces a greater force (thanG machine 2 ) at the same speedmust be comparative, eg a small radius produces a large force = 0 marks on own

1

as the speed increases the rate of change in force increasesaccept force is proportional to the square of the speedordoubling speed, quadruples the forceaccept any clearly correct conclusion

1

(ii) 12000 (N)

or

12 k(N)

1

(c) (i) the current (in the coil) creates a magnetic field (around the coil)accept the coil is an electromagnet

1

so the magnetic field of the coil interacts with the (permanent) magnetic field of the magnets (producing a force)

accept the two magnetic fields interact (producing a force)if no marks scored an answer in terms of current is perpendicular to the (permanent) magnetic field is worth max 1 mark

1

(ii) vertically downwards arrow on side Aone arrow insufficient

and

vertically upwards arrow on side C1

(iii) the current is parallel to the magnetic fieldallow the current and magnetic field are in the same directionallow it / the wire is parallel to the magnetic field

1

(d) increase the current / p.d. (of the coil)accept decrease resistanceaccept voltage for p.d.accept increase strength of magnetic field / electromagnet

1

(e) yes with suitable reasonorno with suitable reasonegyes – it has increased our knowledgeyes – It has led to more (rapid) developments / discoveries (in technology / materials / transport) accept specific examplesno – the money would have been better spent elsewhere on such things as hospitals (must quote where, other things not enough)no mark for just yes / noreason must match yes / no

1[12]

M22.(a) A1

(b) (i) 9000an answer of 9 k(N) gains 1 mark

1

(ii) increase

accept other comparative terms, eg give a biggeraffect / change is insufficient

1

(iii) smalleraccept other comparative terms, eg less

1

(c) Q N Mall three in correct boxesone statement in correct box gains 1 mark

2

(d) any two from:

• increase the current / p.d. (supplied to the coil)accept reduce the resistance of the coil or increase cross sectional area of wireaccept more cells / batteries or turn up the power supplyincrease power is insufficient

• increase number of turns (on the coil)

• increase the area (of the coil)accept increase the width of the coilincrease width / size is insufficient

• increase the (strength of the permanent) magnetic fieldaccept move the magnets closer to the coilaccept use stronger magnetsdo not accept use larger magnets

2

(e) an economic1

[9]

M23.(a) north (pole)accept N

north (pole)both needed for mark

1

(b) reversesaccept changes direction

1

(c) (i) first finger:(direction of) (magnetic) field

1

second finger:(direction of) (conventional) current

1

(ii) into (plane of the) paper1

(iii) less current in wireaccept less current / voltage / more resistance / thinner wire

1

weaker fieldallow weaker magnets / magnets further apartdo not accept smaller magnets

1

rotation of magnets (so) field is no longer perpendicular to wire1

(d) (i) reverse one of the magnetsdo not accept there are no numbers on the scale

1

(ii) systematic or zero erroraccept all current values will be too bigaccept it does not return to zeroaccept it does not start at zero

1[10]

E1. Foundation Tier

Most candidates gained some credit on this question, with the better candidates producing very good descriptions. Some chose simply to describe what they could see in the two diagrams rather than describe the sequence of events that would cause the circuit to break. Incorrect ideas that were frequently seen were that, ‘the coils heat up’, ‘the springs pass the current’ or ‘the button must be pressed to switch off the electricity’. Very few candidates understood that as a consequence of an increased current the electromagnetic attraction increases and attracts the iron bolt.

Higher Tier

Most candidates gained credit on this question, with the better candidates producing very good, detailed descriptions. Some weaker candidates chose simply to describe what they could see in the two diagrams rather than describe the sequence of events that would cause the circuit to break. There were, however, only a few candidates who understood that as a consequence of an increased current, the electromagnetic attraction increases and attracts the iron bolt.

E2. The weaker candidates found difficulty in gaining marks, their writing was not coherent and lacking in relevant detail. Of the more able candidates a surprisingly large number had clearly studied the diagram, worked out how it worked and then offered reasonably precise answers to gain three or four of the marks.

E4. In part (a)(i) very many candidates had the wire moving, unfortunately in many cases the movement was up or down. Few candidates stated that the wire would move along the copper wires to the right. In part (ii) many had the movement reversed, but reversing an up/down movement does not give a correct answer only answers stating that the wire would move to the left were acceptable. In the last part of the question a faster movement was the common correct answer. In part (b) candidates seemed to be familiar with the electric motor but experienced difficulty in applying their ideas in an unfamiliar situation. Most candidates started their answer with a clockwise movement for one mark, fewer went on to say the coil would then vibrate backwards and forwards for the second mark. The final mark, for stating (in their own words) that the coil would end up perpendicular to the field, was gained by a small number of candidates. Part (c) was quite well answered with most candidates scoring marks for increasing the number (or number density) of turns and the current. many went on to gain the third mark for the use of a soft iron core.

E5. Foundation Tier

This question was poorly answered. In this question few could name the switch or explain the operation of a relay in the car starter motor circuit. Common errors included the belief that the electromagnet became ‘charged’ or that a current would flow from the coil to the iron arm and subsequently into the motor.

Higher Tier

In part (i) many candidates were unable to name the switch as a relay. In part (ii) many candidates were able to explain the process by which the car starter ignition system worked, although the precision of the answers was sometimes poor. A significant minority of candidates seemed to think that the iron arm would conduct electricity into the motor circuit.

E6. In part (a)(i) the better candidates gave the correct direction of movement, however, many suggested the wire would oscillate back and forth. Part (a)(ii) was very poorly done. Only a very small number of candidates mentioned the magnetic field created by the current and even fewer indicated any interaction between the fields. Many candidates seemed to interpret the question as ‘how do you work out where the wire moves?’

E7. Foundation Tier

The responses in part (a) was mostly worthy of credit.

(b) There were abundant clues in both the stem of the question and the labels on the diagram to start candidates on the correct sequence. However, rather too many candidates started their answers with the iron bolt moving upwards with the result that they were unable to logically explain the working of the circuit breaker.

Higher Tier

This question was particularly well answered by most candidates.

(a) Most candidates gained both marks in this part but some gave heat insulation and failed to mention electrical insulation.

(b) There were some excellent answers to this part but a minority of candidates were unable to explain how this type of circuit breaker works.

E8. (a) A third of candidates gained the mark by recognising the correct transformer.

(b) A third of candidates knew that a.c. stands for alternating current.

(c) (i) Most candidates recognised that when a current flows in a coil, the coil becomes a magnet.

(ii) Two thirds of candidates gained both marks by recognising that the coil attracts the iron bolt which moves upwards.

E9. (a) Most candidates chose ‘increase the current’ or a correct way of doing this, such as to increase the p.d. or increase the number of cells, and some also suggested ‘have a stronger magnet’. However writing ‘have a bigger magnet’ did not gain credit as a bigger magnet would not necessarily be stronger and the poles could be further from the conductor.

(b) Some candidates correctly suggested that the battery would need to be connected the other way round or that the magnet would need to be put the other way round. However some answers were so poorly expressed that it was impossible to be reasonably sure what

was being suggested.

(c) Few candidates knew that there would be no force on the conductor when the conductor is parallel to the magnetic field or, put another way, when the lines of magnetic force and the path of the electricity do not cross.

E10. (a) A large majority of the candidates chose the correct four appliances from the list.

(b) (i) The responses in part (b) were generally poor with only a minority able to gain a mark in (b)(i) with a similar, though improved, outcome in part (b)(ii).

(ii) Candidates should be advised that although ‘use more cells in the battery’ is correct in part (b)(ii) the ambiguous ‘use a bigger battery’ is not.For similar reasons the vague responses of ‘use bigger magnets’ and ‘use a bigger coil’ were not awarded marks.

E14. (a) Under half of candidates were able to name the effect being demonstrated.

(b) (i) The majority of candidates managed a correct response, although a number of responses needed to be read through a few times as ideas were not expressed clearly.

(ii) The majority of responses were correct.

E15. (a) & (b) Nearly all candidates were able to do the first two items.

(c) (i) & (ii) Many candidates failed to read this correctly and gave answers in terms of magnets which had been precluded in the first sentence of the item. Only a quarter of candidates gained the mark in (c)(i), and even fewer obtained the mark for (c)(ii).

E16. (a) (i) Although over half of candidates knew that the experiment worked because copper is an electrical conductor, just under half of candidates thought it was because copper is a magnetic material.

(ii) Nearly three quarters of candidates were able to describe an acceptable way to increase the speed of the copper roller. However in this question and the next many candidates suggested tilting the rails to achieve the desired effect.

(iii) Candidates lost marks in this question by not explaining clearly enough what they meant, for example several mentioned moving the battery to the other side without mentioning reversing the current or the connections and there were many incorrect answers relating to the switch. However, more than two fifths of candidates gained at least one mark. The most common correct answer related to reversing the magnetic field in some way.

(b) (i) This was well answered with nearly all candidates gaining the mark.

(ii) This was well answered with nearly two thirds of candidates giving the correct type of issue.

E17. (a) (i) Candidates continue to have difficulty in identifying electromagnetic devices. However, half of the candidates correctly identified the motor, whilst a third of candidates thought it was a generator and a small minority of candidates a transformer.

(ii) Nearly three-quarters of candidates identified the force exerted as being the cause of the spin.

(b) A number of candidates wrote down what needed to be changed but often not how they should be changed ie ‘change the number of turns on the coil’ rather than ‘increase the number of turns on the coil’ and so failed to gain credit. Candidates continue to use inappropriate adjectives eg ‘bigger’ magnets rather than ‘stronger’ magnets.

(c) Only a fifth of candidates could give two correct changes. Again poor / inappropriate use of language stopped many candidates gaining any marks.

E18. (a) (i) Students rarely included the idea of the current producing a magnetic field around the wire XY. Some students were clearly confused with the induction process.

(ii) Just over half of students scored this mark.

(iii) Just over half of students scored at least one mark. Incorrect responses included: back and forth; spinning; faster; repelled instead of ‘up and down’. The frequency of 5 hertz was sometimes interpreted as once every five seconds.

(b) There was a clear distinction in this question between the students who could do the calculation perfectly and those who struggled. Some answers were left as fractions by students without calculators; there were a number of 1 mark responses for calculating the left hand moment. A number of students did not gain marks because of inconsistent units and moving between cm and m.

E19.(a) Half the students gained only one mark, often for the “spinning” of the magnet. There was little sequencing of the generator effect.

(b) Nearly three quarters of students gained the mark. Of the remainder, there were still many responses referring to “bigger” magnets rather than ‘stronger magnets’ and “more coils” rather than ‘more turns on the coil’.

E20.Nearly three quarters of students answered part(a) correctly. In (b)&(c), although better answered than in previous series, students continue to have difficulties describing accurately what changes need to be made to a motor to cause different effects. Some still only state what needs to be changed without specifying in what way it is changed, in many of the answers the descriptions were too vague to merit a mark.

E21.(a) The majority of candidates gained both marks on this question. Common errors were “centrifugal” or “centripedal”.

(b) (i) Very few candidates scored all 3 marks, but half of the candidates scored 2. Some mistakenly stated that force changed the speed, rather than understanding that the speed of rotation affected the centripetal force on the astronaut.

(ii) Two thirds of candidates calculated the correct answer.

(c) (i) The majority of responses gained a mark of zero. Use of correct terminology, e.g. the permanent magnetic field interacting with the magnetic field produced by the current, should be stressed to candidates.

(ii) Only a quarter of candidates gained this mark where Fleming’s Left Hand Rule had to be applied. Some failed to gain the mark as they drew in how the coil would rotate, rather than the direction of the forces.

(iii) A quarter of candidates gained this mark. There were a lot of incorrect answers showing the misconception that the upwards and downward forces were equal and opposite.

(d) Two thirds of candidates gained this mark. Of the candidates who did not score, many failed to realise that what was required was an immediate change that the operators could make, or were too brief with their answer “increase the supply”.

(e) This question tested the societal aspects of scientific evidence. Many coherent answers

were produced, with the majority of the responses gaining the mark. At times answers were too brief, “the money would be better spent elsewhere”, rather than stating exactly where (e.g. medical care / hospitals). Some answers looked at possible future benefits, rather than the benefits achieved so far.

E22.(a) Half of the candidates correctly identified the direction of the centripetal force.

(b) The vast majority were able to score all the marks in (b)(i), (b)(ii) and (b)(iii).

(c) About two thirds of candidates correctly placed all three letters; but a significant minority failed to gain marks here.

(d) Around half the candidates scored both marks, but a common mistake was referring to the power supply rather than an increase in p.d. or current. Some candidates failed to score by referring to the use of ‘bigger’ magnets or a ‘bigger’ magnetic field.

(e) The vast majority of candidates gained this mark.

E23.(a) Just over half of the students knew that a magnetic field of repulsion between two poles with lines of force moving outward from the poles was that between two north poles.

(b) Nearly all students knew that reversing the current through a wire also reversed the direction of the field lines associated with it.

(c) (i) Three-quarters of students knew which directions the first two fingers represent in Fleming’s left-hand rule.

(ii) Students were given a diagram of a wire carrying a current in a magnetic field. Using Fleming’s left-hand rule the wire would move into the paper. Many students were able to use the rule successfully, but their answers were ambiguous, such as ‘downwards’ and ‘away from you’. Less than a fifth of students scored the mark.

(iii) Over three quarters of the students knew that decreasing the current and the strength of the magnetic field would decrease the force acting on the wire. Only a tenth of the students knew that rotating the magnets so that the field was no longer perpendicular to the wire would also have the same effect.

(d) (i) Most students observed that two south poles facing each other would not give a uniform magnetic field and suggested that one of the magnets should be rotated.

(ii) Less than three quarters of students knew that an ammeter pointing to a value above zero when no current was in it, had a systematic or zero error.

· Web viewP3 10 Motor Effect Exam Questions 154 minutes 154 marks Q1. Circuit breakers help to...

Documents

Transcript of · Web viewP3 10 Motor Effect Exam Questions 154 minutes 154 marks Q1. Circuit breakers help to...