Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Magnetic monopoles do not exist. Reason (R): Magnetic field lines are continuous and form closed loops. In the light of the 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)

Magnetic Properties of Matter PYQ — JEE Main 2025 · 7 Apr · Shift 2 · Q65 with Solution

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Correct answer: A

Interpret the statements
- Assertion (A): Magnetic monopoles do not exist.
- Reason (R): Magnetic field lines are continuous and form closed loops.
Check Assertion (A)

In classical electromagnetism, isolated magnetic poles have not been observed. A magnet always has both north and south poles.

Also, Gauss's law for magnetism states: $\nabla \cdot \mathbf{B} = 0$ which implies that there are no isolated magnetic charges (monopoles) in ordinary magnetic theory.

Hence, Assertion (A) is correct.
Check Reason (R)

Magnetic field lines never start or end at a point; instead, they form continuous closed loops.

This is consistent with: $\oint \mathbf{B} \cdot d\mathbf{A} = 0$ meaning the net magnetic flux through any closed surface is zero.

Hence, Reason (R) is also correct.
Does (R) explain (A)?

Yes. If magnetic monopoles existed, magnetic field lines would begin on a north monopole and end on a south monopole, just like electric field lines begin and end on charges.

But since magnetic field lines are always continuous closed loops and do not begin or terminate, this supports the fact that magnetic monopoles do not exist.

Therefore, (R) is the correct explanation of (A).
Evaluate the options
- A: Both (A) and (R) are correct and (R) is the correct explanation of (A) ✅
- B: (A) is not correct but (R) is correct ❌
- C: (A) is correct but (R) is not correct ❌
- D: Both (A) and (R) are correct but (R) is not the correct explanation of (A) ❌

The correct option is A.

View written solutionFree

Correct answer: A

Interpret the statements
- Assertion (A): Magnetic monopoles do not exist.
- Reason (R): Magnetic field lines are continuous and form closed loops.
Check Assertion (A)

In classical electromagnetism, isolated magnetic poles have not been observed. A magnet always has both north and south poles.

Also, Gauss's law for magnetism states: $\nabla \cdot \mathbf{B} = 0$ which implies that there are no isolated magnetic charges (monopoles) in ordinary magnetic theory.

Hence, Assertion (A) is correct.
Check Reason (R)

Magnetic field lines never start or end at a point; instead, they form continuous closed loops.

This is consistent with: $\oint \mathbf{B} \cdot d\mathbf{A} = 0$ meaning the net magnetic flux through any closed surface is zero.

Hence, Reason (R) is also correct.
Does (R) explain (A)?

Yes. If magnetic monopoles existed, magnetic field lines would begin on a north monopole and end on a south monopole, just like electric field lines begin and end on charges.

But since magnetic field lines are always continuous closed loops and do not begin or terminate, this supports the fact that magnetic monopoles do not exist.

Therefore, (R) is the correct explanation of (A).
Evaluate the options
- A: Both (A) and (R) are correct and (R) is the correct explanation of (A) ✅
- B: (A) is not correct but (R) is correct ❌
- C: (A) is correct but (R) is not correct ❌
- D: Both (A) and (R) are correct but (R) is not the correct explanation of (A) ❌

The correct option is A.