Question 184 of 311

A point charge $2\times {10}^{–2}C$ is moved from $P$ to $S$ in a uniform electric field of $30N{C}^{–1}$ directed along positive $x$-axis. If coordinates of $P$ and $S$ are $(1,2,0)m\text{and}(0,0,0)m$ respectively, the work done by electric field will be

A$1200mJ$B$600mJ$C$-600mJ$D$-1200mJ$

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Answer: (C) $-600mJ$

As electric field is uniform, so force acting on the charged particle will be uniform.
Therefore,
${W}_{E}=\vec{F}\cdot \vec{s}=q\vec{E}\cdot \vec{s}$
$=\left(2\times {10}^{-2}\right)\left[30\hat{i}\cdot \left[\left(0\hat{i}+0\hat{j}+0\hat{k}\right)-\left(\hat{i}+2\hat{j}+0\hat{k}\right)\right]\right]$
$=-60\times {10}^{-2}J$
$=-600mJ$