AQA AS Level Physics Paper 2, June 2022: Question 5

1 mark · Medium difficulty · Multiple Choice

Identify which row has the largest value for the ratio of the specific charge of the particle in column X to the specific charge of the particle in column Y.

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Question

Multiple choice question 05 asking to identify which row has the largest value for the fraction formed by the specific charge of the particle in column X divided by the specific charge of the particle in column Y. Below is a table with four rows (A to D) and two columns (X and Y) containing different particles: electron, alpha particle, and proton. Row A has electron in column X and alpha particle in column Y; row B has alpha particle in X and electron in Y; row C has electron in X and proton in Y; row D has proton in X and alpha particle in Y.
Question text

05 Which row has the largest value for

specific charge of the particle in column X

?

specific charge of the particle in column Y

[1 mark]

X Y

A electron alpha particle

B alpha particle electron

C electron proton

D proton alpha particle

Mark scheme

Show the mark scheme Mark scheme showing that the correct answer for question 05 is option A, corresponding to column X having an electron and column Y having an alpha particle.

Question Key Answer

05 A (AO1) electron alpha particle

How to answer it

Comparing Specific Charge Ratios

Question 0.5 • Particles and Radiation • 1 Mark
What this question tests:

This question assesses your understanding of specific charge (charge-to-mass ratio), the ability to recall or calculate specific charge values for fundamental particles and nuclei, and how to evaluate fractional ratios between them.

Question 05 Analysis

Determining the Largest Ratio

✅ Correct Answer

Row A: X = electron, Y = alpha particle

Mark Awarded: 1 / 1 mark (AO1)

💡 Key Knowledge

  • Definition: Specific charge = charge / mass (units: C kg⁻¹).
  • Electron: Extremely small mass (~9.11 × 10⁻³¹ kg) paired with a full elementary charge, giving it the largest specific charge of any particle.
  • Alpha Particle: Comprises 2 protons and 2 neutrons with a relatively large mass (~6.64 × 10⁻²⁷ kg), giving it a very small specific charge.

🧠 Exam Technique

Instead of calculating exact numerical values for every option, look at the structure of the fraction: specific charge of X / specific charge of Y . To make this ratio as large as possible, you need the numerator (X) to be as large as possible and the denominator (Y) to be as small as possible.

❌ Common Errors

Students often invert the ratio mentally or confuse protons with alpha particles. Another common trap is forgetting that electrons have a massive charge-to-mass ratio due to their negligible mass, leading candidates to incorrectly choose rows featuring protons or nuclei in column X.

📐 Step-by-Step Breakdown (Why Row A Wins)

  1. Identify X (Numerator): The electron has the highest specific charge of all standard particles (~1.76 × 10¹¹ C kg⁻¹). Placing it as X maximizes the fraction.
  2. Identify Y (Denominator): The alpha particle has a low specific charge (~4.8 × 10⁷ C kg⁻¹) due to its heavy nucleon mass. Placing it as Y minimizes the denominator.
  3. Evaluate the ratio: Dividing a maximum value by a minimum value yields the largest possible overall outcome, confirming Row A.

Topics

Physics · 3.2 Particles and radiation

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.