Question

A flat circle of radius 18 cm is placed in a uniform electric field of magnitude 5.8×10² N/C. What is the electric flux through the circle when its face is: 

1. perpendicular to the field lines

2. 45° to the field lines and

3. parallel to the field lines?

Answer 1

$$\Phi=EA\cos{\alpha}$$

1)

$$\Phi=\pi(0.18)^2(580)\cos{0}=59\ Vm$$

2)

$$\Phi=\pi(0.18)^2(580)\cos{45}=42\ Vm$$

3)

$$\Phi=\pi(0.18)^2(580)\cos{90}=0\ Vm$$