Question

The magnetic force acting on a charged particle of charge $-2\mu C$ in a magnetic field of $2T$ acting in $y$-direction, when the particle velocity is $(2\check{i}+3\check{j})\times 10^{6}m{s}^{-1}$ is :

• A. 4 N in z direction
• B. 8 N in y direction
• C. 4 N in z direction
• D. 8 N in z direction

Answer 1

Answer: (D)

Force on a moving charge in magnetic field $=q(\vec{v}\times B)$
$\Rightarrow \vec{F}=-2\times 10^{-6}(2\hat{i}+3\hat{j})\times 2\hat{j}\times 10^6$
$\Rightarrow \vec{F}=-2\times 10^{-6}(2\hat{i}\times 2\hat{j})\times 10^6$
$\Rightarrow \vec{F}=-8\widehat{kN}$