AQA AS Level Physics Paper 2, June 2024: Question 26

1 mark · Medium difficulty · Multiple Choice

Calculate the reading on a voltmeter connected across a 15 cm section of a 25 cm resistance wire connected to a 6.0 V battery.

Practise this question

Question

A circuit diagram showing a resistance wire XY of total length 25 cm connected across a 6.0 V battery with negligible internal resistance. A voltmeter is connected across a 15 cm central section of the wire, leaving 5 cm segments at each end labelled X and Y. Multiple choice options A (1.8 V), B (2.4 V), C (3.6 V), and D (4.5 V) are listed below.
Question text

26 A resistance wire XY of length 25 cm has constant cross-section.

The wire is connected to a battery of emf 6.0 V and negligible internal resistance.

What is the reading on the voltmeter?

[1 mark]

A 1.8 V

B 2.4 V

C 3.6 V

D 4.5 V

Mark scheme

Show the mark scheme The mark scheme table shows question number 26 with the correct answer option C and the value 3.6 V.

26 C 3.6 V

How to answer it

Question 26: Potential Divider Circuit Study Guide

What this question tests

This question assesses your understanding of potential divider circuits, specifically how voltage is distributed across a uniform resistance wire in direct proportion to its length. You must combine knowledge of circuit principles with proportional reasoning to find the voltmeter reading.

Question Part: Multiple Choice (1 Mark)

Resistance Wire Potential Divider

✅ Correct Answer

C (3.6 V)

Awarded for correctly identifying option C.

💡 Key Knowledge

  • For a wire of constant cross-sectional area and uniform material, resistance is directly proportional to length (R = rho * l / A).
  • In a simple series circuit (or across segments of a single uniform wire), potential difference divides in the exact same ratio as resistance (and therefore length).
  • The total length of wire XY is the sum of all segments: 5 cm + 15 cm + 5 cm = 25 cm.

📐 Step-by-Step Calculation

  1. Identify total length and voltage: Total length = 25 cm , Total voltage = 6.0 V .
  2. Identify length across the voltmeter: The voltmeter is connected across the middle 15 cm segment of the wire.
  3. Set up the ratio: Voltage = (Length of segment / Total length) × Total voltage
  4. Substitute values: Voltage = ( 15 / 25 ) × 6.0 V
  5. Calculate result: Voltage = 0.60 × 6.0 V = 3.6 V .

🧠 Exam Technique

Don't waste time calculating the actual resistance or current of the wire. Because resistance is proportional to length, you can work entirely in ratios of lengths, which saves time and avoids intermediate rounding errors in multiple-choice questions.

❌ Common Errors

  • Using terminal lengths: Students sometimes mistakenly use the 5 cm end sections instead of the 15 cm middle section, yielding 1.2 V (or combining ends to get 10 cm, yielding 2.4 V , which is option B).
  • Miscalculating total length: Forgetting to add all three segments together ( 5 + 15 + 5 ) and accidentally using 15 cm or 20 cm as the denominator.

Topics

Physics · 3.5 Electricity

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.