AQA A-Level Physics Paper 2, June 2025: Question 13

1 mark · Easy difficulty · Multiple Choice

Determine the expression for the change in electric potential energy when a particle of charge q is moved through a potential difference V.

Practise this question

Question

Question 13 asks: 'A particle has mass m and charge q. The particle is moved a distance d through a potential difference V. What is the change in electric potential energy?' Four options are given: A is qV, B is V/q, C is qV/d, and D is V/(qm). Each option has a selection box beside it. The question is worth 1 mark.

Mark scheme

Show the mark scheme Mark scheme for question 13 indicates that the correct answer is option A, which corresponds to qV, assessing AO1.

How to answer it

Work Done & Electric Potential Energy in an Electric Field

📋 What this question tests

This question assesses your understanding of fundamental electric field definitions (AO1 recall and application):

  • The formal definition of potential difference ( V ) as work done per unit charge.
  • The direct relationship between work done ( ΔW ) and change in electric potential energy ( ΔEp ).
  • The ability to identify relevant variables and disregard distractors ( m and d ).

Question 13

Multiple Choice • 1 Mark • Assessment Objective AO1

✅ Correct Answer

A  |  qV

By definition, work done to move a charge q across a potential difference V is given by ΔW = qV .

Since work done equals the change in electric potential energy, ΔEp = qV .

💡 Key Knowledge

  • Potential Difference ( V ): Defined as the energy transferred per unit charge:
    V = ΔW / q
  • Work Done & Energy: Moving a charge against or along an electric field transfers energy:
    ΔEp = ΔW = qV
  • Independence of Distance: When the potential difference V between two points is already known, the distance d between them does not affect the total work done.

📐 Step-by-Step Derivation

  1. Identify given quantities:
    Charge = q , Potential difference = V , Mass = m , Distance = d .
  2. Recall the defining equation for potential difference:
    V = ΔW / q
  3. Rearrange for work done ( ΔW ):
    ΔW = q × V
  4. Relate to electric potential energy:
    Work done on the particle directly equals the change in electric potential energy:
    ΔEp = qV

❌ Common Traps & Distractors

  • Selecting C ( qV / d ): Students confuse energy with electric force. Electric field strength is E = V / d , and force is F = qE = qV / d . The option represents force, not energy!
  • Selecting B ( V / q ): Inverting the definition of potential difference ( V = W / q incorrectly rearranged as W = V / q ).
  • Selecting D ( V / (qm) ): Trying to incorporate mass m . Mass is completely irrelevant to the change in electrostatic potential energy.

🧠 Examiner Technique & Strategy

  • Identify Redundant Information: Examiners frequently provide unnecessary parameters (here, mass m and distance d ) to test whether you truly understand which physical quantities dictate electric potential energy.
  • Check Dimensions/Units:
    • qV has units of C × V = J (Joules, energy) → Valid
    • qV / d has units of J / m = N (Newtons, force) → Invalid
  • Speed Tip: This is a standard 10-second AO1 recall question. Spot W = qV instantly and move on to save time for Section A calculation-heavy questions.
Mark Scheme Breakdown: 1 Mark awarded for option A ( qV ).

Topics

Physics · 3.5 Electricity · 3.7 Fields and their consequences (A-level only)

Question and mark scheme from the AQA A-Level Physics examination, Paper 2, June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.