Q1. [1] § 12.1 MAGNETIC FIELD AND FIELD LINES § 12.2.2 Right-Hand Thumb Rule
Assertion (A) : Magnetic field lines around a bar magnet never intersect each other.
Reason (R) : Magnetic field produced by a bar magnet is a quantity that has both magnitude and direction.
- (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
- (C) Assertion (A) is true, but Reason (R) is false.
- (D) Assertion (A) is false, but Reason (R) is true.
Previously asked in CBSE board exam
2025 31/3/1 Q19
Generated by claude-sonnet-4-6 · 2026-06-15 06:48 · grounding rag
Model Answer
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Field lines don't intersect because at any point of intersection the compass needle would point in two directions simultaneously, which is impossible — not because the field has both magnitude and direction.
Explanation
- A is true: Field lines never intersect — stated directly in the textbook.
- R is true: Magnetic field does have both magnitude and direction (it is a vector quantity) — also stated in the textbook.
- R does NOT explain A: The real reason lines don't cross is that a field can have only one direction at any point. The vector nature of the field is a general property, not the specific cause of non-intersection. Hence option (B).
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