Question

(30-Q2a) shows an imaginary cube of edge L/2. A uniformly charged rod of length L moves towards the left at a small but constant speed $\nu .$ At t = 0, the left end just touches the centre of the face of the cube opposite it. Which of the graphs shown in the figure (30-Q2b) represents the flux of the electric field through the cube as the rod goes through it?

Answer 1

(d)

At first, when the rod is inserted into the cube, the flux start increasing. When the rod is fully inserted, the flux becomes constant and remains constant for the remaining L/2 length of the rod. After that, as the rod moves out of the cube, the flux starts decreasing. These processes are depicted only by curve (d).