A circular parallel-plate capacitor has plate radius R and is being charged by a constant current I. Assuming a uniform electric field between the plates, the displacement current enclosed by a concentric circular surface of radius r < R is:
Options

Question

A circular parallel-plate capacitor has plate radius R and is being charged by a constant current I. Assuming a uniform electric field between the plates, the displacement current enclosed by a concentric circular surface of radius r < R is:

Options

G1 Physics · Accepted Answer

Because the electric field is uniform, the displacement-current density is uniform over the plate area. Total displacement current through area πR² = I. For a concentric circular surface of radius r, enclosed displacement current = I(πr²/πR²) = I(r²/R²). Therefore the correct expression is I(r²/R²). Correct option: C.