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

Options

A. `20 NC^(-1) m^(2)`
B. `30 NC^(-1) m^(2)`
C. `10 NC^(-1) m^(2)`
D. `40 NC^(-1) m^(2)`

Answer

A

Explanation

Here, `E = 2 xx 10^3 NC^(-1)` is along + x-axis.
Surface area, `s = (10 cm)^2 = 10^(2) xx 10^(-4) m^(2) = 10^(2) m^(2)`
When plane is parallel to yz plane, `theta = 0^(@)`
So, `phi = Es costheta = 2 xx 10^(3) xx 10^(-2) cos 0^(@) = 20 NC^(-1) m^(2)`