DP Physics (last assessment 2024)

Question 21M.2.SL.TZ2.3b.ii

Date	May 2021	Marks available	[Maximum mark: 2]	Reference code	21M.2.SL.TZ2.3b.ii
Level	SL	Paper	2	Time zone	TZ2
Command term	Determine	Question number	b.ii	Adapted from	N/A

b.ii.

[Maximum mark: 2]

21M.2.SL.TZ2.3b.ii

A vertical wall carries a uniform positive charge on its surface. This produces a uniform horizontal electric field perpendicular to the wall. A small, positively-charged ball is suspended in equilibrium from the vertical wall by a thread of negligible mass.

(b.ii)

The charge on the ball is 1.2 × 10⁻⁶C. Determine σ.

[2]

Markscheme

$E = \frac{0.14}{1.2 \times 10^{- 6}} « = 1.2 \times 10^{5} »$ ✓

$σ = « \frac{2 \times 8.85 \times 10^{- 12} \times 0.14}{1.2 \times 10^{- 6}} » = 2.1 \times 10^{- 6} « {C m}^{- 2} »$ ✓

Allow ECF from the calculated F in (b)(i)

Award [2] for a bald correct answer.

Syllabus sections

Core

Core » Topic 5: Electricity and magnetism » 5.1 – Electric fields

Core » Topic 5: Electricity and magnetism

Question 21M.2.SL.TZ2.3b.ii

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