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Compiled by

Imran Mirza

MSc Physics,

PGCC, Scoland, Uk

+923336515500

CAMBRIDGE INTERNATIONAL EXAMINATIONS

2013-2014

A-level Physics This booklet covers CIE A Level Physics Paper 5 Imran Mirza

Planning

Analysis

And

Evaluation

Exam tips for Planning, Analysis and Evaluation paper

By

Imran Mirza

Don't rush........

Three golden rules........

1. Read the question

2. READ the question

3. Answer the question

Make sure that you do not do what so many students do......they see a 'key c word like 'magnetic

flux' in a question and write down everything they know about magnetic flux, as fast as they can.

Take your time..........there is more than you think!

IT is forbidden...........

Marks will not be awarded to answers which are unclear. Try to write a reason for your choice of

apparatus and.....

Don't be intimidated........

Don't be intimidated by long questions...... they quite often are easier and quicker questions than

the shorter ones...........

Do as you are told!

Write the apparatus along with reason. Remember that not all of the apparatus in the

provided list is essential for the investigation- You may use other standard equipment that is

needed/ available in the laboratory work.

Draw a neat and labeled diagram of the arrangement of apparatus which you propose to

use. Space is available for this in the question paper.

Write procedure in steps wise and high light control of certain variables to carry out a valid

investigation.

Write the safety aspect (where appropriate) of your investigation. Sometimes the question

specifically ask for these to be mentioned (e.g. in a design question where radioactive sources

are used) but any relevant safety point can be rewarded.

A number of marks are reserved for what is considered to be good further or relevant detail.

This is because your answers depend so much on the approach which has been taken!

Keep in mind!

Some students write copious amounts about the 'conclusions* of their investigation and draw

sketch graphs of what the result might be. Since no experimental work has actually been carried out

it is not possible to reward any work of this kind

Good marks can often be gained by giving relatively short concise answers. Keep

an eye on the time (watch)

Blank paper does not score

Do not leave anything out! If you have no idea what the question is on about....... GUESS. You

never know.... You just might be right! .........and don't give up........ Work right through to the end

of the exam. Cross checking your answers......... keep thinking........ New ideas may draw!

Stay Cool......

Nobody knows everything..........

.......so don't panic if a question is not well answered.

........just do what you can........

The important thing is that you walk out at the en4 thinking......... I DID MY BEST

Things You Should Know For Physics Paper 5: Design, Analysis and Planning VARIABLES

Scientists use an experiment to search for cause and effect relationships in nature. In other words, they

design an experiment so that changes to one thing causes something else to vary in a way that the scientist

can describe as a 'trend'. The most useful way to describe a trend is a mathematical one.

These changing quantities are called variables, and an experiment usually has three main kinds:

independent, dependent, and controlled.

The independent variable is the one that is changed by the scientist. In an experiment there is only one

independent variable. This is usually plotted on the X-axis of the graph that the scientist uses to display

his/her results in.

As the scientist changes the independent variable, he or she observes what happens.

The dependent variable changes in response to the change the scientist makes to the independent

variable. The new value of the dependent variable is caused by and depends on the value of the

independent variable. For example, if you turn on a water tap (the independent variable), the quantity of

water flowing (dependent variable) changes in response - the water flow increases. The more open the tap

- the faster the flow of water. The number of dependent variables in an experiment varies, and there is

often more than one.

Experiments also have controlled variables. Controlled variables are things that would have an effect on

the dependent variable. S/he must be sure that the only thing affecting that variable is his/her adjustment to

the independent variable.

So, controlled variables are quantities that a scientist needs to keep constant, and s/he must observe them

as carefully as the dependent variables.

For example, if we want to measure how much water flow increases when we switch on a tap, it is

important to make sure that the water pressure from the water supply (the controlled variable) is held

constant. That's because both the water pressure and the opening of the tap valve have an impact on how

much water flows. If we change both of them at the same time, we can't be sure how much of the change in

water flow is because of the faucet opening and how much because of the water pressure.

Most experiments have more than one controlled variable. Some people refer to controlled variables as

"constant variables."

INTRODUCTION

Whenever you design an experiment you have to first 'set the scene'.

You are not ever finding anything out without any preconceptions. You always have ideas about

what you are going to find out - you have expectations!

In a science experiment these expectations will be based on:

- what you have experienced in life,

-experiments you have carried out before and

-scientific knowledge (things you have been taught about science at school, or have found out

from books).

In your report you need to explain to the reader what you expect to find out and why!

You do not have to look into a crystal ball and write down numeric predictions... just predict a

general trend. A good way to do this is to sketch a graph!

You do have to explain the main scientific ideas that your prediction is based on. Try to

use scientific keywords in this section and explain in simple terms what you understand them to

mean.

A Fair Test

A fair test situation is vital for an investigation's results to be meaningful. You therefore have to

use the scientific knowledge you have explained toidentify the variables in your investigation -

things you have to control, otherwise it will not be a fair test. Say what will need to be

controlled and why - using theory to explain it.

One of the variables will be the variable you are going to change. Say which on you are going

to change and by how much (the range over which you will change it). Say how you found out

that was a suitable range. It may well be your preliminaries that helped you decide on a suitable

range! Then say have you are going to control all of the others you have identified.

Your fair test must be linked to your scientific knowledge.

PRELIMINARY READINGS

You will have a rough idea of what you want to do, but will need to 'tweak' your idea by trying

things out practically. You therefore sketch out a rough experiemental procedure and test out the

best way to do it in a preliminary session.You may want to:

- choose materials to work with: check that you will get a big enough range of readings with the

ones you have chosen to investigate.

- find out if you are controlling the other variables well enough to have a 'fair test'.... maybe you

will spot some you hadn't thought of!

- practise using the equipment, and see if you need to make adjustments to avoid or minimise

errors.... or make it safer!

- spot dangers in your procedure that you ought to avoid.

Always check with a teacher before you carry out preliminary experiments - they have

more experience at spotting potential dangers than you do!!

What you find out from your preliminary readings will influence your final design of your

experiment.

Remember to say in your report if you found out a better way to do it from preliminary work....

and how you checked your ideas were sound before proceeding.

PROCEDURE

The procedure has several parts to it:

A fully labelled diagram of the experimental equipment.

This should be so detailed that a person could carry out the experiment just from the diagram! It must be fully labelled with specifications of the equipment (e.g. '250 ml beaker' rather than just 'beaker'). Measuring instuments must have their range as well as increments marked on them (e.g. rather than 'thermometer' you would put a mercury filled thermometer with a range of -10

oC to 110

oC in 0.5

oC

increments) A full side of A4 should be given to this!

A full list of equipment - including minor parts

This should be done on a separate sheet of paper as a list to be given to a technician. Full specifications of the equipment (e.g. '250 ml beaker' rather than just 'beaker') must be requested. Measuring

instuments must have their range as well as increments marked on them (e.g. rather than 'thermometer' you would put

a mercury filled thermometer with a range of -10oC to 110

oC in 0.5

oC increments).

Odds and ends such as: 4 connecting wires, 2 croc clips, sellotape etc. must be itemised.

A risk assessment

List all of the possible hazards you have identified and how you intend to avoid them.

A set of instructions

These should be in past impersonal tense.... 'The apparatus was set up as shown in the diagram. The beaker was filled

with 100 ml water..... etc.'. This is far better than a list of instructions with bullet points - but you may want to start off

with such a list and then translate it into the correct form of English for scientific writing. The order must be logical! Don't forget to say that the experiment was repeated, how many times it was repeated etc. Remember to say that results were recorded - in a table of whatever, averaged, and that a graph was plotted.

RESULTS/ANALYSIS

When successive measurements of the same quantity are repeated there is a distribution of values obtained. In experimental physics it is vital to be able to measure and quantify this uncertainty. The words "error" and "uncertainty" are often used interchangeably by physicists - this is not ideal - but get used to it!

Some important questions can only be answered if, in addition to performing an experiment, an

error analysis has been conducted. These include:

Do the results agree with theory?

Are they reproducible?

Has a new phenomenon or effect been observed?

Types of Error

We need to identify the following types of errors:

Systematic errors - these influence the accuracy of a result

Random errors - these influence precision

Mistakes - bad data points.

Accuracy and Precision

These are two terms that have very different meanings in experimental physics. We need to be able to distinguish between an accurate measurement and a precise measurement. An accurate measurement is one in which the results of the experiment are in agreement with the accepted value. Note this only applies to experiments where this is the goal measuring the speed of light, for example. A precise measurement is one that we can make to a large number of decimal places.

ERRORS

These cause reading to be different from the true value. For example; Error is a measure of how close you can be sure about your measurement.

Percentage error = (smallest measurement you can measure/your measurement)*100

e.g. a ruler in mm divisions measure es a length of 10 mm. The smallest that the ruler can measure is to within 0.5 mm. So the error in my measurement of 10mm is;

(0.5 mm/10 mm ) x 100 = 5%

This means I have measured 10 mm +/- 5% The measurement may actually have been as big as 10.5 mm or as small as 9.5 mm.

Types of Errors

- Random

Random errors may be detected and compensated for by taking a large number of readings.

For example: Random errors may be caused by human error, a faulty technique in taking the measurements, or by faulty equipment. These cause readings to be spread about some value other than the true value; in other words, all the readings are shifted one way or the other way from the true value.

- Systematic

These cause readings to be spread about some value other than the true value; in other words, all the readings are shifted one way or the other way from the true value.

- Zero

For example: A zero error occurs when a needle on an ammeter fails to return to zero when no current flows, or when a top-pan balance shows a reading when there is nothing placed on the top-pan balance.

Physics Paper 5 : Sample Solution Q) The Properties of many magnetic materials are affected by temperature. One effect is the loss of permanent magnetism when the temperature of the magnetic material exceeds a particular value. This Temperature is known as the Curie Point. Design an experiment to investigate how the magnetic field strength of a magnet depends on the temperature of the magnet in the range from 0-200 degree Celsius. (May/June 2002) Sol:- Apparatus: 1)Tongs

2) Rubber gloves and protective goggles

3) engine oil ( boiling point > 250 degree Celsius)

4) Digital Thermometer

5) Calibrated Hall Probe with Tesla Meter and a permanent steel magnet

6) Trough

7) Electric Heater with thermostat

8) Dry ice and an insulated container for its storage

Variables:

Independent: Temperature would be the independent variable since its effect on magnetic flux density need to be

observed and will be changed by the observer.

Dependent: Flux density

Control: To ensure a fair test, make sure no other magnetic material is near the apparatus setup; Carry out the

experiment at room temperature. Also the distance of hall probe should be constant from the magnet, otherwise

different values would be obtained for the same temperature and fair test cannot be ensured.

Procedure :

Fill the trough with engine oil and insert the probe/sensor of digital thermometer in it. First add dry ice and let the

temperature fall to 0 degree celsius. Now immerse the permanent steel magnet inside the oil and allow it to remain in

for 10 minutes. Add the dry ice after every 2-3 minutes to ensure the temperature is maintained at 0. After the time

period , take out the magnet with tongs and position the hall probe w/ tesla meter such that it is normal to magnetic

flux. Record the value of flux density obtained and repeat the procedure for the same temperature. Now turn on the

electric heat and maintain temperature at 50 degree C. Immerse the magnet, repeat the same procedure and calculate

the value of flux density obtained. Repeat it for temperatures of 100, 150 and 200 degree C besides that for 0 and 50

which has already been done.

Tabulate the results obtained :

Temperature/*C (Flux Density/T)1 (Flux Density/T)2 (Flux Density/T)Avg

0

50

100

150

200

Draw a graph of Flux Density ( Y-axis) against Temperature( X-axis) Observe the general trend of the plotted line. If a general decreasing trend is obtained , preferably linear such that it meets the x-axis at a specific point (Curie point) , the relationship is proved. Improvements and Safety Concerns Always wear the protective goggles and rubber gloves to prevent damage in case the bubbling oil spills. Handle the magnet with tongs due to temperature extremities. Allow magnet to reach thermal equilibrium ( which is why it is kept in a steady temp for some time) to ensure uniform temperature distribution. Only then measure the flux density with hall probe. As stated above perform the experiment away from any magnetic material that might distort the values for flux density.

Q1. A fine wire mesh has individual wires that are spaced very close together. See flg. 1.1.

Fig. 1.1

The mesh behaves like two diffraction gratings placed at right angles to each other. The diffraction grating formula is d sin = n

The spacing between the wires of the mesh is to be found accurately. Design a laboratory experiment using light of a single wavelength to determine the spacing between the wires. You may assume that the wavelength of the light is known.

You should draw a detailed labeled diagram showing the arrangement of your apparatus. In your account you should pay particular attention to

(a) the type of light source to be used, giving a reason for your choke, (b) the procedure to be followed and the measurements that would be taken, (c) how the measurements would be used to find values of 0, (d) how the spacing between the wires would be deduced, (e) any safety precautions you may take.