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Date May 2017 Marks available 3 Reference code 17M.3.SL.TZ2.3
Level Standard level Paper Paper 3 Time zone Time zone 2
Command term Compare and contrast Question number 3 Adapted from N/A

Question

State one prediction of Maxwell’s theory of electromagnetism that is consistent with special relativity.

[1]
a.

A current is established in a long straight wire that is at rest in a laboratory.

A proton is at rest relative to the laboratory and the wire.

Observer X is at rest in the laboratory. Observer Y moves to the right with constant speed relative to the laboratory. Compare and contrast how observer X and observer Y account for any non-gravitational forces on the proton.

 

[3]
b.

Markscheme

the speed of light is a universal constant/invariant
OR
c does not depend on velocity of source/observer

electric and magnetic fields/forces unified/frame of reference dependant

[1 mark]

a.

observer X will measure zero «magnetic or electric» force

observer Y must measure both electric and magnetic forces

which must be equal and opposite so that observer Y also measures zero force

 

Allow [2 max] for a comment that both X and Y measure zero resultant force even if no valid explanation is given.

[3 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Option A: Relativity » Option A: Relativity (Core topics) » A.1 – The beginnings of relativity

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