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When a rod moves perpendicular to a magnetic field at constant velocity, the FREE charges in the rod experience a force such that:
APositive charges feel no force
BCharges accumulate at the ends, producing an EMF
CCurrent flows continuously even in open circuit
DAll charges feel the same force as the rod
Answer & Solution
Correct answer: B. Charges accumulate at the ends, producing an EMF
1. The qv×B force pushes positive and negative charges to opposite ends of the rod.
2. Charge accumulates until the resulting ELECTRIC field cancels the magnetic force on further charges.
3. The static charge separation creates a potential difference (EMF) across the rod ends.
4. With a closed circuit, this EMF drives a current; in open circuit only the EMF exists.
_Source: NCERT Class 12 Physics Ch 6 §6.6 Motional EMF (microscopic view)_
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