Question

A uniform electric field $E = 2 \times 10^3\, N\, C^{-1}$ is acting along the positive $x$-axis, the flux through the same square if the line normal to its plane makes a $60^°$ angle with the $x$-axis is

• A. $30\, N\, C^{-1}\, m^2$
• B. $10\, N\, C^{-1}\, m^2$
• C. $20\, N\, C^{-1}\, m^2$
• D. $25\, N\, C^{-1}\, m^2$

Answer 1

Answer: (B)

When normal to the plane makes an angle of $60^°$ with $x$-axis, then $\theta = 60^°$
$\phi=Es\,cos\theta=2\times10^{3}\times10^{-2}\,cos\,60^{°}=10\,N\,C^{-1}\,m^{2}$