Question

A charge is fired through a magnetic field. The force acting on it is maximum when the direction of motion of the charge and magnetic field is :

• A. zero
• B. $\frac{\pi }{4}$
• C. $\frac{\pi }{2}$
• D. $\pi$

Answer 1

Answer: (C)

If the charged particle is moving in a magnetic field $\vec{B}$, with a velocity $\vec{v}$ it experiances a force given by,
$\vec{F}=q(\vec{v}\times \vec{B})=$ qvB $\sin \theta$
where, $\theta$ is the angle between $v$ and $B$
If $\theta =\pi /2$ therefore, sin $\pi /2=1$
Hence, $F=$ qvB
The magnetic force acting on it is maximum when the angle between the direction of motion and
magnetic field is $\pi /2$