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

Insulating ball will reach the earth's surface earlier than the metal ball

Metal ball will reach the earth's surface earlier than the insulating ball

Both will reach the earth's surface simultaneously.

Time taken by them to reach the earth's surface will be independent of the properties of their materials

Electromagnetic Induction PYQ — JEE Main 2023 · 31 Jan · Shift 1 · Q50 with Solution

View written solutionFree

Correct answer: C

Identify the physics involved

Since the topic is electromagnetic induction, the key idea is that a metallic ball moving through the Earth's magnetic field can have induced currents (eddy currents) set up inside it.

An insulating ball does not allow such currents to flow.
Effect on the metallic ball

As the metallic ball falls with velocity $\vec v$ through the Earth's magnetic field $\vec B$ , charges inside it experience magnetic force, and circulating currents can be induced.

By Lenz's law, the induced effects oppose the motion that produces them. So the metallic ball experiences a small retarding electromagnetic force upward.

Therefore, its downward acceleration becomes slightly less than $g$ .
Effect on the insulating ball

The insulating ball cannot sustain eddy currents, so there is no such electromagnetic retarding force.

Hence it falls essentially with acceleration $g$ .
Compare times of fall
- Metallic ball: acceleration $< g$
- Insulating ball: acceleration $= g$
Therefore, the insulating ball reaches the ground earlier.
Check options
- A: False — metallic ball is slower, not faster.
- B: False — times are not exactly equal because electromagnetic retardation acts on the metal ball.
- C: True — insulating ball reaches earlier.
- D: False — time does depend on material properties here.
Final answer

The correct option is: $\boxed{\text{C}}$
Comparison with stored answer

Stored correct answer is C, which matches the derived answer.

View written solutionFree

Correct answer: C

Identify the physics involved

Since the topic is electromagnetic induction, the key idea is that a metallic ball moving through the Earth's magnetic field can have induced currents (eddy currents) set up inside it.

An insulating ball does not allow such currents to flow.
Effect on the metallic ball

As the metallic ball falls with velocity $\vec v$ through the Earth's magnetic field $\vec B$ , charges inside it experience magnetic force, and circulating currents can be induced.

By Lenz's law, the induced effects oppose the motion that produces them. So the metallic ball experiences a small retarding electromagnetic force upward.

Therefore, its downward acceleration becomes slightly less than $g$ .
Effect on the insulating ball

The insulating ball cannot sustain eddy currents, so there is no such electromagnetic retarding force.

Hence it falls essentially with acceleration $g$ .
Compare times of fall
- Metallic ball: acceleration $< g$
- Insulating ball: acceleration $= g$
Therefore, the insulating ball reaches the ground earlier.
Check options
- A: False — metallic ball is slower, not faster.
- B: False — times are not exactly equal because electromagnetic retardation acts on the metal ball.
- C: True — insulating ball reaches earlier.
- D: False — time does depend on material properties here.
Final answer

The correct option is: $\boxed{\text{C}}$
Comparison with stored answer

Stored correct answer is C, which matches the derived answer.