Answer to Question #301492 in Electricity and Magnetism for Kent

Question

A flat surface of area 1.25 m2 is rotated through a uniform horizontal electric field of 5 N/C. What is the electric flux if the surface is (a) parallel and (b) perpendicular to the electric field?

Answer 1

Solution

Area

A=1.25m^21.25m²

Electric field E=5N/C

Electric flux is given by

$\phi=EAcos\theta$

a) when parallel then angle is 0°

So cos °=1

So flux

$\phi=5*1.25*1=6.25Wb$

b) when perpendicular then angle will be 90° so cos 90°=0

Therefore flux will be zero.