G6 Answer Key Physiccs WS

8/17/2019 G6 Answer Key Physiccs WS

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Q1.

(a) A wooden pencil is sharpened at both ends. It is connected to two bulbs and a battery as shown. Thetwo crocodile clips are connected to the wooden part of the pencil. Why do the two bulbs not light up?

A: The battery is connected the wrong way round.

B: The bulbs are connected the wrong way round.

C: The wood is a conductor.

D: The wood is an insulator.

1 mark

(b) The two crocodile clips are now connected to the 'lead' (graphite) of the pencil as shown. The two bulbs light up dimly. Why do the two bulbs light up?



1 mark

They light up because graphite is a conductor of electricity - not a good one but it does conduct. That

means we now ha!e a complete circuit.

The reason why the bulbs are only dim is that graphite is a poor conductor.

(c) "ne crocodile clip is connected to the pencil 'lead' (graphite) and the other one is connected to the

wood. Which of the bulbs if any lights up?

#either will light up

1 mark

Maximum 3 marks

Q

#i$$i tries to set up four electric circuits.

(a) In this diagram the ammeter reading is %ero. What is wrong with this circuit?



There is a wire missing between the battery and the bulb

Accept 'there is a wire missing' or 'the bulb is not connected to the battery'

Accept 'it is not a complete circuit'

1 mark

(b) In this diagram the ammeter reading is %ero. What is wrong with this circuit?

&oth wires are connected to one end of the battery cell so the battery cell is not in the circuit.

o not accept 'there is an incomplete circuit'

1 mark

(c) In this diagram the ammeter reading is %ero. Why is this not a complete circuit?



1 mark

The bulb is bro$en or blown or the filament of the lamp is bro$en.

o not accept 'the circuit is not complete'

The circuit is not complete is too !ague - say where the brea$ occurs.

(d) In this diagram why is there a reading on the ammeter?

There is a complete circuit so a current is flowing.

1 mark

Maximum ! marks

Q3.



(a) The drawing below shows the parts of a torch.

(i) aul closed the switch. Why did this turn on the torch?

That action completed the circuit so a current could flow in the bulb.

1 mark

(ii) raw a labelled series circuit for the torch. se the correct symbols for the bulb battery of two cells

and the switch and clearly label each one.

one for each correct labelled symbol



one for the series circuit - no gaps between symbols*

! marks

(b) The drawings below show two other torches. In both torches the bulbs will not light e!en when aul

closes the switches. +oo$ carefully at the drawings.

(i) Why is the circuit of torch A not complete?

The filament of the bulb is bro$en causing a gap within the bulb itself.

1 mark

(ii) What could you do to torch & to get the bulb to light?

Turn one of the cells round - the positi!e terminals are connected together the positi!e should

connect to a negati!e.

1 mark

(c) When aul bought his torch there was a paper strip between the contacts of the switch as shown

below. aul had to remo!e the paper strip before he could turn the torch on. ,i!e the reason for this.



aper is an insulator so it pre!ents the current flow.

1 mark

maximum " marks

Q!. Alice connects four light bulbs for her model house as shown. he puts the bulbs into the holes in

the bac$ wall.

(a) When Alice turns the switch on the bulbs do not light up. The batteries are not flat. #one of the

bulbs is bro$en. Why do the bulbs not light up?

There is not a complete circuit. he needs to add a wire to connect the top left bulb to the bottom left

bulb.



1 mark

(b) Alice ma$es the circuit wor$. When she turns the switch on the bulbs are not !ery bright. What must

Alice add to the circuit to ma$e the bulbs brighter?

Add another electric cell to the battery " connect the bulbs in parallel instead of in series.

1 mark

(c) The four bulbs in the circuit are the same. Which statement is correct?

A: #ach $ul$ is the same $rightness

B: /ach bulb is of a different brightness

C: The bulbs at the top are brighter

D: The bulbs at the bottom are brighter

1 mark

The diagrams show two ways to wire the model house.

(d)

(i) In circuit 0 bulb & brea$s and goes out. What happens to the other bulbs in this circuit?



They all go out

If there is a brea$ in a strand of a circuit no current flows in the whole of that strand.

1 mark

(ii) In circuit 1 bulb 2 brea$s and goes out. What happens to the other bulbs in this circuit?

There is no change in their brightness they all stay lit.

/ach of the bulbs is independently connected across the battery. It therefore has the full potential

difference across it to ma$e a current flow.

1 mark

(e) In circuit 1 Alice adds another switch so that she can turn bulb A off while the other bulbs stay on.

Write the letter '' on circuit 1 to show where Alice should add the switch.

The letter must drawn onto or close to the wire in the top part of the circuit 0 anywhere between the

two 3unctions. (see diagram)

1 mark

Maximum % marks

Q&. A pupil ma$es some electrical circuits. /ach circuit contains a motor and a bu%%er.

The motor and the bu%%er can be switched on or off by three switches A & and 2.

4or each circuit diagram state whether5

(i) the motor is on or off

(ii) the bu%%er is on or off.

(a)



(i) the motor is on

(ii) the bu%%er is on

1 mark

(b)

(i) the motor is off

(ii) the bu%%er is off.

1 mark

(c)



(i) the motor is on.


1 mark

(d)


(ii) the bu%%er is on.

1 mark

(e)





1 mark

Maximum & marks

Q%. hre$ bought two sets of lights to put on a tree in his garden. 2ircuit diagrams for the two sets of

lights are shown below.



(a) What name is gi!en to circuits in which components are connected as in circuit A?

eries circuits

(b) What name is gi!en to circuits in which components are connected as in circuit &?

arallel circuits

(c) If one of the bulbs 'blows' in circuit A what would you obser!e happen to the other bulbs in the

circuit?

All of the other bulbs would go out because there would no longer be a complete circuit

(because there is a brea$ in a filament thread).

(d) If one of the bulbs 'blows' in circuit & what would you obser!e happen to the other bulbs in the



circuit?

The other bulbs would remain on - they would still be at the same brightness as before.

Q'.The diagram shows a circuit for controlling an electric motor. This circuit can ma$e the motorturn forwards or bac$wards.

2omplete the table to show which lamp if any is lit and in which direction if any the motor turns.

(witch A (witch B )hich lamp* i+ an,* is lit- Motor direction +orwards or $ackwards/

up down +amp 0 forwards

up up #one lit #ot mo!ing

down up +amp 1 bac$wards

down down #one lit #ot mo!ing

0 mar$ for each correct row

I ha!e redrawn the circuits for you with the switches in each position to show you that the table is

correct. A thic$ red line mar$s out the complete circuit in each case.



This is the sample one. It shows you which way the current has to be flowing for the motor to mo!e'forward'.

#o battery in the circuit - so no current will flow.



#o current here either - no battery in the circuit.

The current flows the opposite way now - so the motor will be in re!erse.

3 marks

Q". 6ohn connects up the circuit shown below.

The bulb is not bright enough. 7is friend suggests four circuits which could be used to ma$e the bulb



brighter.

(a) Which is the correct circuit to use5 A & 2 or ?

2ircuit A

1 mark

#e8t 6ohn sets up circuit / and notes the reading on the ammeter.

7e then places another bulb in the circuit to ma$e circuit 4.



7e notes the ammeter reading in circuit 4.

(b) 7ow will the ammeter reading in circuit 4 compare with that in circuit /? /8plain your answer.

The reading in circuit 4 will be lower than that of circuit /. The voltage from the power supply will

be

shared by the bulbs in circuit F. The current flow will thererfore be lower. " the resistance in the

strand has increased - therefore the current

will be less.

The current would only 'hal!e' if the resistance of a bulb was constant. The filament in a lamp gets hotter

as

the current through it increases. This means that as you increase the !oltage across a bulb the current

will

increase but not by as much as you might e8pect - this means it has an increased resistance.

A 'dim' bulb has a lower resistance than a brightly lit one. ee here for more detail.

marks

(c) raw a circuit diagram in which two bulbs are lit as brightly as the bulb in circuit / and the ammeter

reading is the same as in circuit /.

To light two brightly in series you need an additional power supply as they will share the !oltage from

http://www.cyberphysics.co.uk/topics/electricity/basic_electricity/characteristics.htm

http://www.cyberphysics.co.uk/topics/electricity/basic_electricity/characteristics.htm



the battery.

In parallel an additional strand will ha!e the full !oltage from the power supply. 9a$e sure you put the

ammeter in a position that measure the current through one bulb - do the combinattion current as shown

below.

1 mark

Maximum ! marks

Q0. ressure pads can be used to set off burglar alarms. The alarm is set off when someone steps

on the pad. The alarm wor$s by sounding a bu%%er or switching on a lamp or both.

The symbols for a pressure pad is5

7ere are fi!e circuit diagrams. +oo$ carefully at the fi!e circuit diagrams.



Tic$ the correct bo8 in the table below to show what is happening in each circuit.

Circuit

Diagram

he $u22er is on

and the lamp is

o++

he lamp is on

and the $u22er

is o++

Both the $u22er

and the lamp are

on

he $u22er and

the lamp are $oth

o++

A

B

C

D

#

& marks

Q1. In the circuit abo!e both the bulbs light up. uddenly they both go out. The two bulbs are

tested. &ulb A wor$s but bulb & is bro$en.



(a) &ulb A was not bro$en but it went out. Why did it go out?

&ulbs A and & are in series. The brea$ in the filament of bulb & ser!es as a brea$ in the circuit. :ou

need a complete conducting loop for a current to flow. The brea$ means than no current flows so the

lamp A goes out too.

1 mark

In the circuit below only bulb & is bro$en.

(b)

(i) oes bulb A light up? :es

1 mark

(ii) oes bulb 2 light up? :es

1 mark

Maximum 3 marks

G6 Answer Key Physiccs WS

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