Question

An electric field \(3\hat{j} + 4\hat{k}\) N/C is present at a place. What will be the electric flux passing through a square plate if the plate is placed in the y-z plane?

(a) 7 Nm^2C^-1

(b) 25 Nm^2C^-1

(c) Zero

(d) 17 Nm^2C^-1

I have been asked this question by my college director while I was bunking the class.

This intriguing question comes from Gauss’s Law topic in chapter Charges and Fields of Physics – Class 12

Answer 1

The correct answer is (c) Zero

The explanation: The electric field is present in the y-z plane. So, if we place a square surface in the y-z plane, the area vector of the plane will be perpendicular to the electric field and hence cos⁡θ becomes 0 as θ is 90 degrees. So, E*surface area*cosθ becomes zero i.e. no flux through the surface.