Question

A particle of mass $1\times {10}^{-26}$ $kg$ and charge $1.6\times {10}^{-19}$ $C$ travelling with a velocity $1.28\times {10}^{6}m{s}^{-1}$ along the positive $X-$axis enters a region in which there is a uniform electric field $\overrightarrow{E}=-102.4\times {10}^{3}kN{C}^{-1}$ and magnetic field $\overrightarrow{B}=8\times {10}^{-2}\hat{j}Wb{m}^{-2}$ , the direction of motion of the particles is :

• A. along the positive X-axis.
• B. along the negative X-axis.
• C. at ${45}^o$ to the positive X-axis.
• D. at ${135}^o$ to the positive X-axis.

Answer 1

Answer: (A)

along the positive X-axis.

Force acting on the particle when it enters in the electric field & magnetic field is
$F=q\overrightarrow{E}+q\overrightarrow{V}\times \overrightarrow{B}$
$=1.6\times {10}^{-19}\times (-102.4\times {10}^3)\hat{k}+1.6\times {10}^{-19}\times 8\times {10}^{-2}\times 1.28\times {10}^6$
$=0$
It will not deviate from its path. It will continue to move along the positive $x-$axis.