Question

When the electric field is parallel to the surface, what is the angle θ between the field vector and the area vector?

Options

• 0°

• 180°

• 90°

• 45°

Answer 1

When the electric field is parallel to the surface, it is perpendicular to the area vector (which points normal to the surface). Therefore, θ = 90°, and \[\Phi = EA \cos(90°) = 0\]. No electric field lines cross the surface in this configuration.