A conducting bar of length L is free to slide on two parallel… | JEE Main 2021 (16 Mar, Shift 1)

Q42JEE Main 2021 · 16 MAR · SHIFT 1Medium

Motional EMF

A conducting bar of length L is free to slide on two parallel conducting rails as shown in the figure

Two resistors R1 and R2 are connected across the ends of the rails. There is a uniform magnetic field $\vec{B}$ pointing into the page. An external agent pulls the bar to the left at a constant speed v. The correct statement about the directions of induced currents I1 and I2 flowing through R1 and R2 respectively is:

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Answer: (b)

Bar moves left with $\vec{B}$ into the page: force on + charge $q\vec{v} \times \vec{B}$ points down the bar.
So current flows downward in the bar.
Left loop ( $R_1$ ): bar is its right side, downward current there means clockwise (also: its inward flux decreases, so induced current is clockwise).
Right loop ( $R_2$ ): bar is its left side, downward current there means anticlockwise (its inward flux increases).
So the answer is (b) $I_1$ clockwise, $I_2$ anticlockwise.

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