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A metallic conductor with a non-uniform (irregular) cross-section has a constant potential difference applied across its ends (1) and (2). Which of the following statements is correct?

1. The current through cross-section P equals the current through cross-section Q.
2. The electric field at P is less than the electric field at Q.
3. The rate of heat generated per unit time at Q exceeds that at P.
4. The number of electrons crossing per unit area per unit time at P is less than at Q.

Correct answer: The current through cross-section P equals the current through cross-section Q.

Solution

In steady current flow the same current passes through all cross-sections regardless of area; only current density, field, and drift change with area.

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