Electric Charges And Fields Ques 35
35. A square surface of side $L$ metres is in the plane of the paper. A uniform electric field $\vec{E}$ (volt / $m$ ), also in the plane of the paper, is limited only to the lower half of the square surface (see figure). The electric flux in SI units associated with the surface is
[2006]
(a) $E L^{2} / 2$
(b) 0
(c) $E L^{2}$
(d) $E L^{2} /(2 \varepsilon_0)$
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Answer:
Correct Answer: 35.(b)
Solution:
(b) Flux $=\vec{E} \cdot \vec{A}$ is incorrect; the correct formula for electric flux is $\Phi_E = \vec{E} \cdot \vec{A}$.
$\vec{E}$ is electric field vector & $\vec{A}$ is area vector.
Here, angle between $\vec{E}$ & $\vec{A}$ is $90^{\circ}$.
So, $\vec{E} \cdot \vec{A}=0$; Flux $=0$
BETA
