AQA GCSE Physics Physics Paper 1 (Foundation), November 2020: Question 8

11 marks · Standard Demand difficulty · Short Answer

Investigate the I-V characteristics of a filament lamp including circuit setup, graphical analysis, calculating resistance, and defining zero error.

Practise this question

Question

An exam question with 5 parts about a filament lamp experiment. Figure 11 shows a circuit diagram with a power supply, variable resistor, and lamp. Part 08.1 asks to add an ammeter and voltmeter. Figure 12 shows an I-V graph for positive potential differences up to 6V. Parts 08.2 to 08.5 ask to extend the graph for negative values, state Ohm's law / resistance equation, calculate resistance at 1.0 V using the graph, and define a zero error for the ammeter.
Question text

08 A student investigated how the current in a filament lamp varied with the potential

difference across the filament lamp.

Figure 11 shows part of the circuit used.

Figure 11

08.1 Complete Figure 11 by adding an ammeter and a voltmeter.

Use the correct circuit symbols. 30

[3 marks]

Figure 12 shows some of the results.

Figure 12

08.2 The student reversed the connections to the power supply and obtained negative

values for the current and potential difference.

Draw a line on Figure 12 to show the relationship between the negative values of

current and potential difference.

[2 marks]

08.3 Write down the equation which links current (I), potential difference (V) and

resistance (R).

[1 mark]

08.4 Determine the resistance of the filament lamp when the potential difference across it

is 1.0 V.

Use data from Figure 12.

[4 marks]

Resistance = Ω

08.5 A second student did the same investigation. The ammeter used had a zero error.

What is meant by a zero error?

[1 mark]

Mark scheme

Show the mark scheme The mark scheme for Question 8, detailing answers for parts 08.1 through 08.5. It allocates marks for correct ammeter and voltmeter symbols and placement, drawing the symmetrical negative curve on the graph, stating V = IR, calculating R = 12.5 ohms from the graph current value of 0.08 A, and defining zero error as a non-zero reading when not connected.

Question 8

AO /

Question Answers Extra information Mark

Spec. Ref.

08.1 ammeter and voltmeter symbols 1 AO1

correct 4.2.1.1

RPA 4

voltmeter in parallel with lamp 1

ammeter in series with lamp 1

08.2 smooth curved line of correct shape do not accept a line that 1 AO2

becomes horizontal 4.2.1.4

RPA 4

passing through - 4.0 V, - 0.2 A 2nd mark conditional on 1

or scoring 1st mark

– 6.0 V, - 0.23 A

08.3 potential difference = current × 1 AO1

resistance 4.2.1.3

or RPA 4

V = IR

08.4 AO2

I = 0.08 (A) 1 4.2.1.3

RPA 4

1.0 = 0.08 × R allow 1.0 = their I × R 1

provided their I has been

obtained from the graph

1.0 1.0 1

R = allow R =

0.08 their I

R = 12.5 (Ω) allow an answer consistent 1

with their I

Question Answers Extra information Mark AO / 15

Spec. Ref.

08.5 ammeter displays a reading 1 AO3

when not connected (to a circuit) 4.2.1.4

RPA 4

Total 11

How to answer it

Investigating Filament Lamps & Circuit Analysis

What this question tests

This question assesses your practical electrical skills (Required Practical 4), your ability to interpret current-potential difference graphs (including negative values), recall and apply Ohm's Law, and understand meter errors such as zero error.

Question 08.1

Adding Meters to a Circuit Diagram

Complete Figure 11 by adding an ammeter and a voltmeter using correct circuit symbols.

✅ Correct Answers

  • Ammeter symbol drawn correctly and placed in series with the lamp.
  • Voltmeter symbol drawn correctly and placed in parallel across (either side of) the lamp.

💡 Key Knowledge

  • Ammeter: Measures current and must always be placed in series so all the charge flows through it. It has very low resistance.
  • Voltmeter: Measures potential difference (voltage) and must always be placed in parallel across the component. It has very high resistance.

❌ Common Errors

  • Placing the voltmeter in series (this stops current flowing due to its high resistance).
  • Placing the ammeter in parallel across the lamp (causes a short circuit/excessive current).
  • Drawing incorrect shapes for meter symbols (use a circle with an 'A' or a 'V').
Marks available: 3 marks
Question 08.2

Extrapolating Graph Curves (Negative Values)

The student reversed connections to get negative values. Draw a line on Figure 12 showing the relationship for negative values.

✅ Correct Answers

  • A smooth curved line mirroring the positive side through the origin (0,0).
  • The curve must pass neatly through -4.0 V, -0.2 A or -6.0 V, -0.23 A .

🧠 Exam Technique

Treat rotational symmetry through the origin! As potential difference becomes negative, current also becomes negative symmetrically because the resistance behavior of the filament lamp remains identical regardless of current direction.

❌ Common Errors

  • Drawing a straight line instead of a curve.
  • Making the line flatten out horizontally at the ends (do not let it become flat).
  • Failing to pass precisely through the origin (0,0). Note: The second mark is conditional on getting the first mark correct!
Marks available: 2 marks
Question 08.3

Equation Linking V, I, and R

Write down the equation which links current (I), potential difference (V), and resistance (R).

✅ Correct Answers

  • potential difference = current × resistance
  • OR V = I × R (or rearranged equivalents like R = V / I )

💡 Key Knowledge

Ohm's Law / circuit equations must be memorised word-for-word. Avoid writing symbols without defining them unless standard letters like V, I, R are explicitly requested.

Marks available: 1 mark
Question 08.4

Calculating Resistance from a Graph

Determine the resistance of the filament lamp when the potential difference across it is 1.0 V using data from Figure 12.

📐 Step-by-Step Calculation

  1. Step 1: Locate 1.0 V on the horizontal x-axis of Figure 12.
  2. Step 2: Read off the corresponding current (I) from the vertical y-axis. At 1.0 V, current I = 0.08 A (allow values consistent with your reading, e.g., 0.07 to 0.09 A). [1 mark]
  3. Step 3: Substitute values into the rearranged equation: R = V / I → R = 1.0 / 0.08 . [2 marks for equation substitution]
  4. Step 4: Calculate the final value: R = 12.5 ohm . [1 mark]

❌ Common Calculation Traps

  • Misreading the graph grid lines (each small square on the y-axis between 0 and 0.1 represents 0.01 A).
  • Inverting the division (doing current divided by voltage instead of voltage divided by current).
Marks available: 4 marks
Question 08.5

Defining Zero Error

A second student did the same investigation. The ammeter used had a zero error. What is meant by a zero error?

✅ Correct Answers

  • When a measuring instrument displays a non-zero reading when there is no potential difference / when it is not connected to a circuit.
  • A false reading when the true value should be zero.

💡 Key Knowledge

Systematic Error / Zero Error: A type of measurement error caused by equipment not being correctly calibrated to zero before starting. This adds a consistent shift to all readings taken.

Marks available: 1 mark

Topics

Physics · Required Practicals · P2: Electricity · Required Practicals

Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 1 (Foundation), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.