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A charged particle is at rest in a region of uniform magnetic field B. The magnetic force acting on it is:
AMaximum, normal to B
BEqual to qB, directed along B
CEqual to qB, opposite to B
DZero, since v is zero
Answer & Solution
Correct answer: D. Zero, since v is zero
1. The magnetic force is $\mathbf{F} = q(\mathbf{v} \times \mathbf{B})$.
2. Its magnitude is $F = qvB\sin\theta$, which depends on the speed $v$.
3. For a charge at rest, $|\mathbf{v}| = 0$, so $F = 0$.
4. Only a moving charge experiences a magnetic force.
_Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", p.135_
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