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JEE Main 2021 (27 Jul, Shift 1) · Electric Current, Drift Velocity & Current Density

Electric Current, Drift Velocity & Current Density question from JEE Main 2021 (27 Jul, Shift 1)

Q22JEE Main 2021 · 27 JUL · SHIFT 1Medium

Electric Current, Drift Velocity & Current Density

In the given figure, a battery of emf E is connected across a conductor PQ of length 'l' and different area of cross-sections having radii r1 and r2 (r2 < r1).

Choose the correct option as one moves from P to Q:

Show answer and solution

Answer: (a)

The current $I$ is the same at every section of PQ (series path), so (c) is wrong.
From P to Q the area falls ( $r_2 < r_1$ ), so $J = \dfrac{I}{A}$ increases.
$v_d = \dfrac{J}{ne}$ increases and $E = \rho J$ also increases, so (b) is wrong.
So the answer is (a).

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