Exemplar Script 4

1

GCE Physics 2008 marking grids AS – Script 4 A: Summary of case study or physics-based visit Criterion Mark

Ref Criterion

Mark Comment

S1 Carries out a visit OR uses library, consulting a minimum of three different sources of information (eg books/websites/journals/magazines/case study provided by Edexcel/manufacturers’ data sheets)

1 Assuming that the Introduction to Green Chemistry is a journal, then 3 different sources are present

S2 States details of visit venue OR provides full details of sources of information

1 Details of the sources are given

S3 Provides a brief description of the visit OR case study

1 The study of solar cells is clear

S4 Makes correct statement on relevant physics principles

1 Reasonable explanation of how a solar cell works

S5 Uses relevant specialist terminology correctly

1 Correct use of scientific terminology

S6 Provides one piece of relevant information (eg data, graph, diagram) that is not mentioned in the briefing papers for the visit or case study

1 Allowing for the fact that this is photocopied, the diagram of the solar cell is good. Also table of efficiencies is good

S7 Briefly discusses context (eg social/environmental/historical)

1 Environmental factors discussed

S8 Comments on implication of physics (eg benefits/risks)

1 Benefits and costs of solar cells are discussed

S9 Explains how the practical relates to the visit or case study

1 Measurement of the internal resistance of a solar cell in relation to the energy loss in the cell is discussed

Total marks for this section

9

B: Planning

Ref Criterion

Mark Comment

P1 Lists all materials required 1 List of apparatus given P2 States how to measure one relevant

quantity using the most appropriate instrument

1 Ammeter used to measure current

P3 Explains the choice of the measuring instrument with reference to the scale of the instrument as appropriate and/or the number of measurements to be taken

1 Scale to be used on ammeter discussed

P4 States how to measure a second relevant quantity using the most appropriate instrument

1 Voltmeter used to measure voltage (potential difference)

P5 Explains the choice of the second measuring instrument with reference to the scale of the instrument as appropriate and/or the number of measurements to be taken

1 Range to be used on voltmeter discussed

P6 Demonstrates knowledge of correct measuring techniques

1 Changing range is an appropriate measuring technique

2

P7 States which is the independent and

which is the dependent variable 1 Identifies power as the dependent variable and resistance

of the rheostat as the independent variable P8 Identifies and states how to control all

other relevant variables to make it a fair test

0 Identifies temperature of the cell as an important factor but should also comment on light intensity

P9 Comments on whether repeat readings are appropriate in this case

0 Could have repeated the experiment to obtain a second value for the internal resistance. However I and V values cannot be averaged because of different rheostat settings.

P10 Comments on safety 1 Hot lamp considered P11 Discusses how the data collected will be

used 1 Graph of power against resistance and finding resistance

at the point of maximum power transfer P12 Identifies the main sources of

uncertainty and/or systematic error 1 Connection resistance allowed, but light intensity changes

would be a major problem P13 Draws an appropriately labelled diagram

of the apparatus to be used 1 Circuit diagram is correct, although it would have been

preferable to have included some sort of protective resistor or lamp.

P14 Plan is well organised and methodical, using an appropriately sequenced step-by-step procedure

1 Sequenced step by step procedure given

Total marks for this section

12

C: Implementation and Measurements

Ref Criterion

Mark Comment

M1 Records all measurements using the correct number of significant figures, tabulating measurements where appropriate

1 Significant figures used in the table are appropriate

M2 Uses correct units throughout 1 Units correct throughout M3 Obtains an appropriate number of

measurements 1 7 different values of potential difference is sufficient

M4 Obtains measurements over an appropriate range

0 The range of currents and potential differences used seems very small. Could a different resistance rheostat have been used?

Total marks for this section

3

3

D: Analysis

E: Report

Ref Criterion

Mark Comment

A1 Produces a graph with appropriately labelled axes and with correct units

1 Axes labelled and units

A2 Produces a graph with sensible scales 1 Data occupies more than half the page in each direction A3 Plots points accurately 1 The plotted points checked are correct A4 Draws line of best fit (either a straight

line or a smooth curve) 0 The line of best fit consists of parallel lines in some

places. A5 Comments on the trend/pattern

obtained 1 Power increases with resistance, reaches a maximum

point and then decreases with resistance discussed A6 Derives relation between two variables

or determines constant 1 Determines maximum power and resistance at maximum

power A7 Discusses/uses related physics principles 0 No discussion of why the internal resistance is equal to

the external resistance when the power is a maximum A8 Attempts to qualitatively consider

sources of error 1 Changes of light intensity caused by the lamps of other

students are discussed A9 Suggests realistic modifications to reduce

error/improve experiment 0 Far away from other lights is not enough. Would like to

have seen comment on control of incident light A10 Calculates uncertainties 0 Lowest value of resistance at a possible maximum point is

10.0 Ω on the graph, but the candidate uses 9.5 Ω. Hence calculation is not correct

A11 Provides a final conclusion 1 Internal resistance of the solar cell has been found.

Total marks for this section 7

Ref Criterion

Mark Comment

R1 Summary contains few grammatical or spelling errors

0 Summary is difficult to understand in some places and there are spelling mistakes

R2 Summary is structured using appropriate subheadings

1 Subheadings are given in the summary.

Total marks for this section

1

Total marks for this unit

32