Question

Figure shows an imaginary cube of edge L/2. Auniformly charged rod of length L moves toward left at a small but constant speed $\upsilon$. At t=0, left end of the rod just touches the right face of the cube. Which of the graphs in Fig. represents the flux of the electric field through the cube as the rod goes through it?

Answer 1

As the rod enters the box, the charge increases; hence, flux increases linearly. When rod enters the cube completely, the charge within the cube becomes constant for sometimes and hence the flux also becomes constant. When the road starts moving out of the cube, the charge inside the cube starts decreasing and hence the flux will also start decreasing linearly. Hence, graph d is the current graph.