Dissecting A Physics Question : What you should know to get full credit in your answers

Most examination boards require you to know these terms set in the questions:

1. Define (the term(s) ...) is intended literally. Only a formal statement or equivalent
paraphrase, such as the defining equation with symbols identified, being required.

2. What is meant by ... normally implies that a definition should be given, together with some
relevant comment on the significance or context of the term(s) concerned, especially
where two or more terms are included in the question. The amount of supplementary
comment intended should be interpreted in the light of the indicated mark value.

3. Explain may imply reasoning or some reference to theory, depending on the context.

4. State implies a concise answer with little or no supporting argument, e.g. a numerical
answer that can be obtained 'by inspection'.

5. List requires a number of points with no elaboration. Where a given number of points is
specified, this should not be exceeded.

6. Describe requires candidates to state in words (using diagrams where appropriate) the
main points of the topic. It is often used with reference either to particular phenomena or
to particular experiments. In the former instance, the term usually implies that the answer
should include reference to (visual) observations associated with the phenomena.
The amount of description intended should be interpreted in the light of the indicated mark
value.

7. Discuss requires candidates to give a critical account of the points involved in the topic.

8. Deduce/Predict implies that candidates are not expected to produce the required answer
by recall but by making a logical connection between other pieces of information. Such
information may be wholly given in the question or may depend on answers extracted in an
earlier part of the question.

9. Suggest is used in two main contexts. It may either imply that there is no unique answer
or that candidates are expected to apply their general knowledge to a 'novel' situation, one
that formally may not be 'in the syllabus'.

10. Calculate is used when a numerical answer is required. In general, working should be
shown.

11. Measure implies that the quantity concerned can be directly obtained from a suitable
measuring instrument, e.g. length, using a rule, or angle, using a protractor.

12. Determine often implies that the quantity concerned cannot be measured directly but is
obtained by calculation, substituting measured or known values of other quantities into a
standard formula, e.g. the Young modulus, relative molecular mass.

13. Show is used where a candidate is expected to derive a given result. It is important that
the terms being used by candidates are stated explicitly and that all stages in the
derivation are stated clearly. ( courtesy , the CIE syllabus)

While all these may be useful , then again they never tell you how will you be scored and what will you need to write to get full credit in your answers. Going through roughly 20 marking schemes I found one thing common and I can bet that rarely a student knows.

Physics is all about cause and effect , nearly all sciences are governed by a cause and effect relationship. In most free-response questions , you'll see that if you follow the way stated below, you would be able to score full marks in your answer.

1. Comment on the cause.
2. State its effect
3. State the conclusion you came up with.

e.g Why does it appear that a charge on a sphere is concentrated at the centre of the sphere?(CIE 9702/4 May/June 2007)

All the field lines are normal to the sphere (Cause )
Which means that they radiate from a single point and are directed radially outwards ( effect)
So as a result if we extend them they would intersect at a common point i.e the centre of the sphere. Therefore the charge is concentrated at the centre as all the field lines seem to originate from the centre of the sphere. (Conclusion)

So you see this was all to this question. And if you've written all these points by keeping the three points I mentioned ( I call them ' The Key' ) , you'll never lose you're marks (strong statement but honest statement).

I also suggest not to rush on to answering the questions without thoroughly understanding what the question is asking. The Key can be useful but you'll often come across questions that would render this method useless. Don't panic , read the question slowly two-three times and try to grab the central idea. Then in your mind, draft a rough answer. Now frame an answer according to THE KEY in mind and you'll get a hang of it. Try this method, it'll help a lot.

Revise Effectively ( Final Touches )

You all must be thinking what more is there to revision. I can well understand that frustration takes it all and it drains down any signs for motivation. Once you lose it, your mind wanders in wilderness, with the book in front of you, you begin to think about each and everything lest your studies. You should not let this happen. I'm writing all this non-sense because I have been a victim of it , and I don't want you to become one. So whenever you feel demoralized, demotivated, put your book down or whatever it is that you're doing. Close your eyes and just imagine, just imagine yourself on the result day. Imagine you're holding your certificate, with stellar grades and everyone around you is mesmerized, awe-struck, while your teachers are all the more proud of you. Imagine so vividly as if its the way its going to happen. This should give an outright boost for the next few hours.

Now back to business. To give the final touches to your revision, its time to move on to practice actual exam papers. If you're already done with exam papers of your own board, its time to move on to other boards. I'll let you in on a little secret. CIE and OCR have very similar questions. So much so that i practiced OCR chemistry (AS level) MCQs for my CIE A level exams and found that nearly 8 of them were taken from the OCR's previous papers. I was so relieved and happy to see them , and they pretty much saved me a handful of time to go through my paper twice. For those appearing for Cambridge International Examinations (CIE) , doing exam papers from the OCR board after they're finished with their own is a must. If those get finished too, move on to doing Edexcels etc etc. There are 5 boards conducting O and A levels so there's no shortage of practice materials out there :P. Practice until you feel confident that you have an excellent grasp of the syllabus.

I find quite absurd and stupid that some students move on to solve the past papers a few days or just a day before their exams. This is the biggest make a student can make and this is bound to cost him his grade. Please, I repeat please do not leave the past exam papers for the last moment, but solve them at an earlier time, as has been stated in the previous two posts. The last few days before the exam are for you to go through your notes once again and go over the few questions you found the most difficult while you were practicing.

There's not more to revision and I hope I have conveyed all that was required for you to get on revising and revising effectively. If you feel I have left out on anything , then please feel free to give your feedback and I'll make amends in shortest time possible.

Revise Effectively ( 2nd Phase )

By the time you read this, I presume you would have already started off with making effective study notes. If not , do so today!!!!! For those of you who have, its time to move on to the next phase. Once you're done with a preliminary set of notes , do a quick revision. Scan through them, check for any errors, conceptual and grammatical( Trust me you get irritated with wrong spellings, I do!) and try to correct them. Recheck with the syllabus just to make sure you haven't missed out on any learning outcomes. During this period , if you come across any topic you don't understand, don't wait but consult your teacher asap for help.

Finally, you have what it takes to make the grade : Your own study notes. Your own study guide, which trust me will be better than any other book you buy for your final revision just before the exams. It is always wise to keep on memorizing and revising your notes. I used to memorize four or five topics over the weekend and then just before going to bed, make a virtual mind-map with the walls and roof as my virtual pages. Then whenever I was free, I would recite a topic in my heart. This ordeal takes no more than 5 or 6 minutes. I strongly advise you to do the same.

This is it for the 2nd phase , not much to it eh.... but remember to keep on revising and never leave all the revision for the last moment. You should be fully prepared for your exams a month before your exams start.

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.

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 to identify 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 -10^oC 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.

(These have been compiled from various sources including Wikipedia and Cyberphysics )

A look at Physics Paper 5 : Design, Analysis and Planning

First Things First : How to Revise Effectively (1st Phase)

lets kick start with how to revise effectively for your A level exams. Phase 1 of your effective study/revision covers how to study the topic to be learned and includes condensing information from various sources , later to be used as your final revision notes.

1) Study the topic you need to learn very carefully. To that and to make sure that you know each and everything examiner wants you to know, grab a copy of a) Your A level Syllabus and b) Your Syllabus' Scheme of Work. While the Syllabus can be directly downloaded from your examination boards website ( in this case: http://www.cie.org.uk/ ), ask your teacher for a copy of schemes of work. It is designed for teachers to assist them in making their lesson plans but can be of huge benefits to the students themselves if they can get first hand information on what will they be taught. You can also get this from Freeexampapers. With your hands on these, scan through the contents of the topic you plan to study,to get a GIST on what you're supposed to learn. When done pick up atleast 3 different books by different authors to study that topic. Highlight important details and concepts you come across. Work through the examples to get an idea of what type of questions generally come.

2) Once done Studying, read through the highlighted material again and try to combine and condense all the information in a summary form orally.

3) Try to solve past papers questions relating to that topic from at least 10 previous exam papers. It is said that if you go through papers from at least 5 years , you will be well aware of what's going to come in your exam! What better?

4) Finally, its time to make your notes ( Don't worry if you skip this part, I'll be providing notes on nearly every topic with hints and tips that you won't regret :) ). Still if you want to make your notes, organize them in the following fashion:
a) Start with definitions, followed by the central idea of the topic.
b) Clearly mention all theorems, concepts and try to write them in your own words, and in a summarized form.
c) Always draw a margin line at one side ( probably the right) and leave ample space to jot down anything new you come across regarding that topic.
d) MAKE A MIND MAP AT THE END

....And Remember, always practice exam style and exam board questions , even from boards other than your own. Study hard and START WITH ALL THIS 6 MONTHS BEFORE YOUR EXAM!!!!