WJEC Physics for A2: Student Bk

7 About this book Questions in one A level unit will not focus specifically on content from other units but some questions in each exam will draw upon skills and knowledge acquired in studying for other units. For example, the knowledge of conservation of momentum gained in Unit 1 could be required when discussing α and β decay in a Unit 3 examination. Mark allocations The mark allocation for each question part is given in square brackets, e.g. Explain the purpose of damping in a car suspension system. [3] The mark allocation gives a good clue to the detail required in your answer. The [3] is a clue that the examiner will expect you to make three valid points in the answer. Questions involving calculations Depending on their complexity, questions which require the calculation of a result will generally be allocated more than one mark. Unless the question specifically asks for the working to be shown, full marks will normally be awarded for just a correct answer, consisting of a number, a unit and (in the case of vector quantities) a direction. However, incorrect answers will only be given credit for correct stages in the calculation, so you are advised always to show your working. Normally the number of marks available without the correct answer is one fewer than the total allocation. Error carried forward (ecf) This is also referred to as consequential marking . The principle is that the result of a calculation, in one part of a structured question, is treated as correct if it is used in a subsequent part of the same question. It is often not applied within a question part. See the Study and Revision Guide for further discussion of the application of ecf . Command words used in WJEC exam questions Examination ‘questions’ are not usually phrased as questions. They are usually instructions to do some work. Examiners choose the command words carefully so that you understand the sort of answer required. This is a list of the most common command words used. State Give a brief, concise answer with no explanation. For example: State the value of the intercept . For questions which require the value of a quantity to be stated, it is expected that no calculation (or at most a trivial one) is needed. Describe Write a short account with no explanation. For example: Describe the relationship shown in the graph . Experimental methods can also be asked for using this command word. Explain This requires reasons to be given. Depending on the question a description might also be required. For example: Explain which of these samples has the greater activity . In this example the sample with the greater activity has first to be identified (which might not itself be allocated a mark). The explanation might need to include a calculation. Suggest This command word often occurs in the last part of a structured question. There might not be a definite answer but you are expected to put forward a sensible suggestion based upon your physics knowledge. For example: Suggest how you could investigate whether the assumption was correct . Calculate Use one or more equations to find the value of an unknown quantity. For example: Calculate the amplitude of the oscillation . Determine This command word is often used instead of calculate. Give a numerical answer by manipulating data you have been given. There is no absolute difference between the words but determine tends to be used in situations where an additional process is required beyond a calculation. For example: Determine the decay constant of the radioactive sample. In this case you might first need to draw a suitable graph. Compare For example: Compare the heat transfer from the two systems . Make sure that you make a comparison rather than two separate descriptions, e.g. ‘System A has a greater heat transfer than system B.’ Depending on the context, this type of question might require a numerical answer, e.g. ‘The heat transfer from system A is 2.5 × that from system B.’ Discuss This is often used for questions on the practical application of scientific ideas or technological developments. For example: Discuss whether the expenditure on space research is justified . As with suggest there is no correct answer to this type of question. The examiner is looking for reasoned arguments.