KCET 2025 Physics Paper

In a steady-state circuit the charge per second crossing any section must be the same, so the current I is constant. However, for a non-uniform wire:
- Drift speed
vd=‌

I

nqA

depends on the local cross-sectional area A, so vd varies.
- Electric field
E=ρJ=ρ‌

I

A

also varies with A.
Therefore only the current remains the same throughout.
Answer: Option C (Current only).