Question

Electrons having a velocity $\overrightarrow{v}$ of $2\times {10}^{6}m{s}^{-1}$ pass undeviated through a uniform electric field $\overrightarrow{E}$ of intensity $5\times {10}^{4}V{m}^{-1}$ and a uniform magnetic field $\overrightarrow{B}$.
(i) Find the magnitude of magnetic flux density B of the magnetic field.
(ii) What is the direction of $\overrightarrow{B}$, if $\overrightarrow{v}$ is towards right and $\overrightarrow{E}$ is vertically downwards in the plane of this paper?

Answer 1

(i) Given: $v=2\times {10}^{6}m/s$
$E=5\times {10}^{4}V/m$
We know that $v=E/B$
$\therefore$ $B=\frac{5\times {10}^4}{2\times {10}^6}=0.025$T
$=2.5\times {10}^{-2}$T.

(ii) Direction of magnetic field intensity is vertically inside into the plane of paper.