alleryStart learning →A charged sphere is held at rest inside a strong uniform magnetic field. What magnetic force acts on it?
AA force along the field
BA force across the field
CA force twice its weight
DNo magnetic force at all
Answer & Solution
Correct answer: D. No magnetic force at all
1. The magnetic force is F = qvB sin(theta), so it is proportional to the speed v.
2. A charge at rest has v = 0, which makes the force zero.
3. There is no magnetic force on static charges, only on moving ones.
4. The sphere would feel a magnetic force only once it started moving across the field.
_Source: OpenStax College Physics (CC BY 4.0), Ch 22 "Magnetism", section 22.4 Magnetic Field Strength: Force on a Moving Charge in a Magnetic Field_
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