Question

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:

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

Answer 1

The correct option is D Current only

Let E be electric field, then current density $j=\sigma E$
Also we know that current density $j=\frac{i}{A}$
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 $v_d$ is given by $v_d=\frac{j}{ne}=$ different for different j values.Hence only current i remains constant.