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A steady current flows in a metallic conductor of non-uniform cross-section. Which of the following quantities is constant along the conductor?

Asked in GSEB Board March 2022 · Current and charge flow

Answer: (3) current

Step-by-step solution

Idea: for a steady current, charge cannot pile up anywhere, so the same charge crosses every cross-section each second. The current I is the same all along the wire.

Current density j = I/A is larger where the wire is thinner.

Drift speed v_d = I/(neA) is larger where the wire is thinner.

Electric field E = ρ j is also larger where the wire is thinner.

So only the current is constant along the conductor.

Why the other options are wrong

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