Q75 · Practice questionComplex familiar4 marks
QUESTION 75 (4 marks)
A conducting rod moves to the right through a uniform magnetic field directed into the page. Explain why a potential difference develops between the rod’s ends and identify which end becomes positive.
WORKED SOLUTION
4 marksPractice marking scheme
ANSWER
The magnetic force separates charges; for a rod moving right with into the page, positive charge is driven upward, so the upper end becomes positive.
Worked solution
Charges in the moving conductor experience magnetic force . For positive charge, is right and is into the page, so is upward. Electrons experience the opposite force and accumulate at the lower end. Charge separation creates an internal electric field and hence a potential difference. The upper end is positive relative to the lower end.
Links moving charges to magnetic force.
Uses correct force direction for positive charge.
Explains charge separation and potential difference.
Identifies upper end as positive.
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