# A charge Q is moving

Question:

A charge $Q$ is moving $\overrightarrow{\mathrm{dI}}$ distance in the magnetic field $\overrightarrow{\mathrm{B}}$. Find the value

of work done by $\overrightarrow{\mathrm{B}}$.

1. (1) 1

2. (2) Infinite

3. (3) Zero

4. (4) $-1$

Correct Option: , 3

Solution:

(3)

Since force on a point charge by magnetic field is always perpendicular to

$\vec{v}[\vec{F}=q \vec{V} \times \vec{B}] \therefore$ Work by magnetic force on the point charge is zero.