Friday, January 9, 2015

O-Level Physics (5054) | Exam Tips

  • O-Level Physics (5054) | Exam Tips

This post contains tips and advices that highlight some common mistakes made by past candidates. It is intended that these tips will help candidates in their preparation and even when undertaking their upcoming O-Level Physics (5054) exams.

  • There is no escaping it; the best way to prepare for a physics examination is thorough and careful revision.
  • Just reading your notes over and over again is not an efficient way to revise. Make your revision productive by making it interesting and fun. Make notes, revision cards or mind maps. Revision should be an active process, i.e. you should be ‘doing things’, not just sitting and reading a book.
  • Don’t try to learn it all in one go! Not understanding a particular concept at one time does not mean you will never understand it. Do not give up easily! Take regular breaks and review what you have learnt regularly.
  • Learning equations is essential; put them on small pieces of paper and stick them somewhere you will see them every morning.
  • Revise with a friend so you can test each other or try explaining the physics of a topic to a friend – as if you were a teacher! Share your tips with your friend for topics you understand very well and do not hesitate to ask for help from your friends on topics you are less familiar. Do not try to learn on your own.
  • Working through past paper questions is the best way to complete your revision. This helps you to know the type and style of questions to expect in the examination. This also helps you develop your problem solving skills, which are essential for physics.
  • Try timed questions so you can learn to answer quickly.
  • Get your answers checked so you know you are correct!

The spelling of technical terms is important, so make sure your writing is legible as well as spelt correctly. If your writings cannot be read properly, you will lose marks. Some words are very similar, such as reflection and refraction, fission and fusion. Check the spellings of technical terms carefully.

General tips
In Cambridge O Level Physics (5054) examinations candidates have to be able to complete a variety of tasks; always read the question carefully to make sure you have understood what you are expected to do.

Descriptive answers
In descriptive answers, candidates should:
  • Check the number of marks available and make sure you give sufficient points.
  • Plan your answer first so that you don’t repeat yourself or contradict yourself.
  • Read your answer through carefully afterwards to check you have not missed out important words.
  • Read the question again to check you have answered the question asked.
  • Use sketches and diagrams wherever you can to help your explanation.
  • Add labels when referring to a diagram, e.g. point X, so that you can refer to it easily in your explanation. This can save many words and much confusion.

Numerical answers
In numerical answers, candidates should:
  • Quote any formulae you are going to use and show clearly all the steps in your working. It may be tempting to use your calculator and just write down the answer, but if you write down one figure wrongly then you may lose all the marks for the calculation. If the examiners can see the formula and the numbers you have used then you will lose only a little credit. Some questions ask for a formula to be quoted; even if you get the right answer, failure to quote the formula will lose you a mark.
  • Check the units are consistent, e.g. if the distance is given in km and the speed in m/s, then you must convert the km to m.
  • Be careful when you are converting minutes and seconds: 1 minute 30 seconds is not 1.3 minutes and 150 seconds is not 1.5 minutes. These are common mistakes, so always double check any conversion of units of time.
  • State the answer clearly at the end.
  • Give your answer as a decimal to an appropriate number of significant figures. Don’t leave your answer as a fraction unless specifically asked to do so.
  • Check that you have given the unit of your final answer.
  • Look at your final answer and see that it is reasonable. If you have calculated the cost of using an electrical appliance such as a kettle for a few minutes and found it to be hundreds of dollars, then check the powers of ten in your calculation.

Plotting graphs can be tested in Papers 2, 3 or 4 (reading from graphs may be present in Paper 1 too).

When drawing graphs, candidates should:
  • Remember to label the axes with both quantity (e.g. distance or d) and unit (e.g. metres or m). Then write it as distance / metres or even just d / m.
  • Make sure the axes are the correct way round. You are usually told, for example, to plot distance on the x-axis, so make sure you know that x is the horizontal axis!
  • Make the scales go up in sensible amounts, i.e. 0, 5, 10… or 0, 2, 4… but not 0, 3, 6… or 0, 7, 14…
  • Make sure that the plotted points fill at least half the graph paper. This means if you can double the scale and still plot all the points then you should double the scale.
  • Check if you have been told to start the scales from the origin. If not, then think carefully about where to start the axes.
  • When you are told to start the axes from a certain point (e.g. x=1, y=20) you must do so. You will lose a mark if you use a different point (e.g. the origin).
  • Use a sharp pencil to plot the points and draw the line.
  • Plot the points carefully. It is best to use small neat crosses. Every point will be checked by the examiner, and you will lose the mark if any are wrongly plotted.
  • Draw either a straight line or a smooth curve. In physics we never join the dots!
  • Your line may not go through all the points – especially in the practical papers.
  • Remember that a best fit line (curve or straight) should have some points above and some points below the line.

When taking readings from a graph, candidates should:
  • Draw a large triangle when measuring the gradient of a line. It must be at least half the length of the line. Top tip: draw a triangle the full size of the graph! It is best to show the numbers on the sides of the triangle when finding the gradient.
  • Always use points on the line, not your plotted points, when calculating the gradient.
  • Draw a tangent to find the gradient of a curve. Make sure it is at the right place on the curve. Again, use a large triangle.
  • Make sure you read the scales correctly when reading a value from a graph. It may be that they are in mA rather than A or km rather than m.

When describing the shape of a graph, remember that:
  • directly proportional means a straight line through the origin.
There are two ways to check if quantities are directly proportional:
– doubling one quantity will cause the other to double
– dividing one by the other will give the same result
i.e. if two quantities F and L are directly proportional then if you find several values of F/L they should be the same.

  • if the straight line does not go through the origin, then it is just called a linear graph.

  • inverse relationship means increasing one quantity will cause the other to decrease.

  • if doubling one quantity causes the other to halve, then they are inversely proportional.
This can also be checked by:
– multiplying the two quantities together will give the same result
i.e. if two quantities F and L are inversely proportional then if you find several values of F × L they should be the same.

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