Spherical insulating ball and a spherical metallic ball of same size and mass are dropped from the same height. Choose the correct statement out of the following {Assume negligible air friction} (a) Metal ball will reach the earth's surface earlier than the insulating ball (b) Both will reach the earth's surface simultaneously. (c) Insulating ball will reach the earth's surface earlier than the metal ball (d) Time taken by them to reach the earth's surface will be independent of the properties of their materials

Answer: (c). The metal ball moves through the Earth's magnetic field, so small eddy currents can be induced in it. By Lenz's law these oppose its motion, slightly reducing its acceleration. The insulating ball has no eddy currents and falls with g. So the insulating ball reaches earlier, answer (c).

Spherical insulating ball and a spherical metallic ball of same size… | JEE Main 2023 (31 Jan, Shift 1)

Q16JEE Main 2023 · 31 JAN · SHIFT 1Easy

Lenz's Law, Eddy Currents & Induced Electric Field

Spherical insulating ball and a spherical metallic ball of same size and mass are dropped from the same height. Choose the correct statement out of the following

{Assume negligible air friction}

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Answer: (c)

The metal ball moves through the Earth's magnetic field, so small eddy currents can be induced in it.
By Lenz's law these oppose its motion, slightly reducing its acceleration.
The insulating ball has no eddy currents and falls with $g$ .
So the insulating ball reaches earlier, answer (c).

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