Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A : An electric fan continues to rotate for some time after the current is switched off. Reason R : Fan continues to rotate due to inertia of motion. In the light of above statements, choose the most appropriate answer from the options given below.

Both A and R are correct and R is the correct explanation of A

A is not correct but R is correct

A is correct but R is not correct

Both A and R are correct but R is NOT the correct explanation of A

Rotational Motion PYQ — JEE Main 2023 · 10 Apr · Shift 2 · Q41 with Solution

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Correct answer: C

Understand the assertion

Assertion $A$ : An electric fan continues to rotate for some time after the current is switched off.

This is correct. When power is cut off, the fan blades do not stop instantaneously; they keep rotating for a while and gradually come to rest due to friction and air resistance.
Understand the reason

Reason $R$ : Fan continues to rotate due to inertia of motion.

This is also correct. By Newton’s first law, a body in motion tends to remain in motion unless acted upon by an external retarding torque. The rotating fan has rotational inertia, so it continues rotating after the current is switched off.
Check whether the reason explains the assertion

The fan keeps rotating because of its tendency to maintain its state of rotational motion, i.e. inertia. It eventually stops because friction in the bearings and air drag produce a retarding torque.

So, $R$ is the correct explanation of $A$ .
Evaluate the options
- A: $A$ is not correct but $R$ is correct $\,\rightarrow$ False
- B: $A$ is correct but $R$ is not correct $\,\rightarrow$ False
- C: Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$ $\,\rightarrow$ True
- D: Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$ $\,\rightarrow$ False

Therefore, the correct option is C.

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Correct answer: C

Understand the assertion

Assertion $A$ : An electric fan continues to rotate for some time after the current is switched off.

This is correct. When power is cut off, the fan blades do not stop instantaneously; they keep rotating for a while and gradually come to rest due to friction and air resistance.
Understand the reason

Reason $R$ : Fan continues to rotate due to inertia of motion.

This is also correct. By Newton’s first law, a body in motion tends to remain in motion unless acted upon by an external retarding torque. The rotating fan has rotational inertia, so it continues rotating after the current is switched off.
Check whether the reason explains the assertion

The fan keeps rotating because of its tendency to maintain its state of rotational motion, i.e. inertia. It eventually stops because friction in the bearings and air drag produce a retarding torque.

So, $R$ is the correct explanation of $A$ .
Evaluate the options
- A: $A$ is not correct but $R$ is correct $\,\rightarrow$ False
- B: $A$ is correct but $R$ is not correct $\,\rightarrow$ False
- C: Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$ $\,\rightarrow$ True
- D: Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$ $\,\rightarrow$ False

Therefore, the correct option is C.