AQA AS Level Physics Paper 2, June 2023: Question 28

1 mark · Easy difficulty · Multiple Choice

Identify the correct combination of resistance values for an ideal ammeter and an ideal voltmeter.

Practise this question

Question

Multiple choice question 2 8 asking which row shows the resistance of an ideal ammeter and an ideal voltmeter, with four options A, B, C, and D presented in a table. Row A shows zero and zero, row B shows zero and infinite, row C shows infinite and zero, and row D shows infinite and infinite.
Question text

28 Which row shows the resistance of an ideal ammeter and of an ideal voltmeter?

[1 mark]

Resistance of ammeter Resistance of voltmeter

A zero zero

B zero infinite

C infinite zero

D infinite infinite

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer is B, corresponding to zero resistance for an ammeter and infinite resistance for a voltmeter.

28 B zero infinite

How to answer it

Resistance of Ideal Ammeters and Voltmeters

Question 28 • 1 Mark

What this question tests

This question assesses your foundational understanding of circuit components—specifically, how ideal ammeters (used to measure current) and ideal voltmeters (used to measure potential difference) behave within electrical circuits and how their internal resistance affects circuit operation.

Question 28 Breakdown

Identifying the correct properties of ideal meter components

✅ Correct Answer: Option B

Ammerter resistance: zero

Voltmeter resistance: infinite

Awarded 1 mark for selecting row B.

💡 Key Knowledge

  • Ideal Ammeter: Placed in series. It must have zero resistance so it does not alter the total resistance of the circuit or reduce the current it is trying to measure.
  • Ideal Voltmeter: Placed in parallel. It must have infinite resistance so that no current flows through it, ensuring it doesn't divert current away from the component being measured.

🧠 Exam Technique

For quick multiple-choice questions like this, evaluate one component at a time to immediately eliminate incorrect options:

  • Ask yourself: "Does an ammeter want to block current or let it flow freely?" Freely → zero resistance. This eliminates options C and D.
  • Then look at the voltmeter: "Should current go through the voltmeter or stay in the main circuit?" Stay in the main circuit → infinite resistance. This leaves only option B.

❌ Common Errors

Students occasionally confuse the placement and purpose of the meters, mixing up series and parallel rules:

  • Thinking a voltmeter needs low resistance to "read" the voltage easily.
  • Confusing real-world meters (which have small non-zero ammeter resistance and very high, but finite, voltmeter resistance) with theoretical ideal components.

Topics

Physics · 3.5 Electricity

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.