Question

A uniform electric field `E=2xx10^(3)NC^(-1)` is acting along the positive x-axis. The flux of this field through a square of 10 cm on a side whose plane is parallel to the yz plane is
A. `20NC^(-1)m^(2)`
B. `30NC^(-1)m^(2)`
C. `10NC^(-1)m^(2)`
D. `40NC^(-1)m^(2)`

Answer 1

Correct Answer - A
Here, `E=2xx10^(3)NC^(-1)` is along + x-axis
Surface area, `s=(10cm)^(2)=10^(2)xx10^(-4)m^(2)=10^(-2)m^(2)`
when plane is parallel to yz plane, `theta=0^(@)`
So `phi=Escostheta=2xx10^(3)xx10^(-2)cos0^(@)=20NC^(-1)m^(2)`