Q255 · Practice questionSimple familiar3 marks
QUESTION 255 (3 marks)
The diagram shows opposing flat magnet poles, N on the left and S on the right. A straight wire in the central gap carries conventional current out of the page. Treat the central gap field as uniform.
a)[1 mark]
Sketch four field lines in the central gap, including arrowheads.
b)[2 marks]
State and justify the direction of the magnetic force on the wire.
WORKED SOLUTION
3 marksPractice marking scheme
ANSWER
(a) Four parallel, equally spaced arrows from N to S. (b) Up the page.
Worked solution
(a) Away from edge effects, a uniform field is represented by parallel lines at equal spacing, directed from N to S.
(b) The field points right and current points out of the page. The right-hand rule for gives an upward force.
Equivalent physically justified methods, alternative valid sketches and consistent units accepted.
Accept sensible significant figures and consistent rounding from stated constants.
Part a: Draw parallel equally spaced N-to-S field arrows.
Part b: State upward.
Part b: Justify using the conventional-current and field directions in a valid force rule.
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