A Steady current flows in a metalic conductor of non uniform cross section. The quantity/quantities which remain constant along the length of the conductor is/are

Options

A. Current electric field and drift speed
B. Drift speed only
C. Current and drift speed
D. Current only

Answer

D

Explanation

(d) If `E` is the electric field, then current density `J = sigma E`
Also we know that current density `J = (i)/(A)`
Hence `j` is difference for different area of cross-section. When `j` is different, then `E` is also different. Thus `E` is not constant. The drift velocity `v_(d)` is given by `v_(d) = (j)/(n e)`
only current `i` will be constant.