Question

A charged particle moves with velocity v in a uniform magnetic field B. The magnetic force experienced by the particle is ___________.

• A. always zero
• B. zero if B and v are perpendicular
• C. zero if B and v are parallel
• D. zero if B and v are inclined at ${45}^o$

Answer 1

Answer: (C)

zero if B and v are parallel

Magnetic force acting on the charged particle $\overrightarrow{F}=q(\overrightarrow{v}\times \overrightarrow{B})=qvB\sin \theta$
If $\theta =0^o$ $⟹\sin 0^o=0$
$⟹F=0$
Thus, magnetic force is zero if v and V are parallel.