Question

The following table gives the length of three copper wires, their diameters, and the applied potential difference across their ends. Arrange the wires in increasing order according to the following:

(a) The magnitude of the electric field within them,

(b) The drift speed of electrons through them, and

(c) The current density within them.

| Wire no. | Length | Diameter | Potential Difference |
| 1. | L | 3d | V |
| 2. | 2L | d | V |
| 3. | 3L | 2d | 2V |

Answer 1

(i) E1 = V/L, E2 = V/2L, E3 = 2V/3L

E2 < E3 < E1

(ii) Vd α E

Vd2 < Vd3< Vd1

(iii) I = nAe Vd / J= σE

J = n e Vd

J2 < J3<J1