A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/ quantities 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

If E be electric field, then current density `J = sigmaE`
Also we know that current density `j = i/A`
Hence j is different for different area of cross-sections.When j is different, then E is also different.
Thus E is not constant. The drift velocity `v_(d) = j/("ne") =` is given by
j = SE
The j changes due to different for different j values. Hence only current i will be constant.