NEET 2016 Phase 2 · PhysicsLoop centre fieldPrevious Year Question
A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the centre of the loop is B. It is then bent into a circular coil of n turns. The magnetic field at the centre of this coil of n turns will be:
Answer: (B) n²B. Answer: (B) Solution: Wire length is fixed: 2πr = n·2πr′ ⟹ r′ = r/n.
- A.nB
- B.n²B✓
- C.2nB
- D.2n²B
Correct Answer
(B) n²B
Solution & Explanation
Answer: (B) Solution: Wire length is fixed: 2πr = n·2πr′ ⟹ r′ = r/n. One turn: B = μ₀I/2r. n turns: B′ = μ₀nI/2r′ = μ₀nI/2(r/n) = n²·(μ₀I/2r) = n²B. → option B.
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