Question

The magnitude of the magnetic force on a charge is zero when

• A. charge is at rest
• B. charge is moving parallel to the field
• C. charge is moving perpendicular to the field
• D. both when charge is at rest or moving parallel to the field.

Answer 1

Answer: (D)

Magnitude of magnetic force on a moving charge in a external magnetic field is given by
$F =qv \, B \sin \theta$
Here, $F$ will be zero if $v = 0,$ or $\theta = 0^{\circ}$ or $180^{\circ} $