Moving Charges and Magnetism - Result Question 8

8. The magnetic force acting on a charged particle of charge $-2 \mu C$ in a magnetic field of $2 T$ acting in $y$ direction, when the particle velocity is

$(2 \hat{i}+3 \hat{j}) \times 10^{6} ms^{-1}$, is

[2009]

(a) $4 N$ in $z$ direction

(b) $8 N$ in $y$ direction

(c) $8 N$ in $z$ direction

(d) $8 N$ in $-z$ direction

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Answer:

Correct Answer: 8. (d)

Solution:

  1. (d) The magnetic force acting on the charged paraticle is given by

$ \begin{aligned} & \overrightarrow{{}F}=q(\overrightarrow{{}v} \times \overrightarrow{{}B}) \\ & .=(-2 \times 10^{-6})[{2 \hat{i}+3 \hat{j}) \times 10^{6}} \times(2 \hat{j})] \\ & =-4(2 \hat{k}) \\ & =-8 \hat{k} \end{aligned} $

$\therefore$ Force is of $8 N$ along negative $z$-axis.