AQA AS Level Physics Paper 2, June 2024: Question 33

1 mark · Easy difficulty · Multiple Choice

Identify which feature of a potential difference versus current graph for a power supply represents its electromotive force.

Practise this question

Question

Multiple choice question 33 asking which feature of a graph of potential difference against current represents the emf of a power supply, with four options: A the area enclosed by the line and the x-axis, B the magnitude of the gradient of the line, C the intercept on the x-axis, and D the intercept on the y-axis.
Question text

33 A student investigates the characteristics of a power supply.

The experimental data are plotted on a graph with:

• pd (potential difference) across the power supply plotted on the y-axis

• current in the power supply plotted on the x-axis.

The axes intersect at (0,0).

What feature of the graph represents the emf of the power supply?

[1 mark]

A the area enclosed by the line and the x-axis

B the magnitude of the gradient of the line

C the intercept on the x-axis

D the intercept on the y-axis

Mark scheme

Show the mark scheme Mark scheme table showing question number 33 with correct answer D, corresponding to the intercept on the y-axis.

33 D the intercept on the y-axis

How to answer it

Power Supply Characteristics and EMF

AQA AS-Level Physics • Multiple Choice Question

What this question tests

This question assesses your understanding of electromotive force (emf), internal resistance, terminal potential difference equations, and your ability to relate physical equations directly to graphical representations (straight-line graphs of the form y = mx + c ).

Question 3.3

Identifying EMF from a Power Supply Graph

✅ Correct Answer

Option D: the intercept on the y-axis

Marks available: 1 mark

💡 Key Knowledge

  • The equation linking terminal pd ( V ), emf ( E ), internal resistance ( r ), and current ( I ) is: V = E - Ir or V = -rI + E .
  • Comparing this to the linear equation y = mx + c :
    • y -axis = potential difference ( V )
    • x -axis = current ( I )
    • Gradient ( m ) = -r (negative internal resistance)
    • y -intercept ( c ) = E (emf)

🧠 Exam Technique

Always write out the standard physics equation relevant to the circuit or apparatus described, and rearrange it into the algebraic form of a straight line ( y = mx + c ). This immediately tells you what physical quantity each axis, gradient, and intercept represents.

❌ Common Errors

  • Confusing the axes: Students who mix up V and I often mistakenly choose Option C (the x -intercept).
  • Guessing the gradient: Some students think the magnitude of the gradient represents emf, forgetting that gradient corresponds to internal resistance ( r ).

Topics

Physics · Required Practicals · 3.5 Electricity · AS practicals (1–6)

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.