Question: Q. 1. Define the term ’electric flux’. Write its SI unit. What is the flux due to electric field $\vec{E}=3 \times 10^{3} \hat{i}$ $\mathrm{N} / \mathrm{C}$ through a square of side $10 \mathrm{~cm}$, when it is held normal to $\vec{E}$ ? R [Comptt. O.D. I, II, III 2013]
Show Answer
Solution:
Ans. Electric flux is the number of electric field lines passing through a given area.
Its SI unit : $\mathrm{NC}^{-1} \mathrm{~m}^{2}$ or $\mathrm{V}-\mathrm{m}$
Given : $\vec{E}=3 \times 10^{3} \hat{i}$ N/C, $A=(10 \mathrm{~cm})^{2}=0.01 \mathrm{~m}^{2}$ and $\theta=0^{\circ}$
$\phi=E A \cos \theta$
$\phi=E . A=3 \times 10^{3} \times(0.1)^{2}=30 \mathrm{NC}^{-1} \mathrm{~m}^{2}$
[CBSE Marking Scheme, 2013]
