NEET 2021 · PhysicsMutual inductionPrevious Year Question
Two conducting circular loops of radii R1 and R2 are placed in the same plane with their centres coinciding. If R1 >> R2, the mutual inductance M between them will be directly proportional to:
Answer: (B) R₂² / R₁. Answer: (b) Solution: Treat the large loop (R₁) as the source: its field at the centre is B = µ₀I/(2R₁), nearly uniform over the tiny inner loop (R₂).
- A.R₁² / R₂²
- B.R₂² / R₁✓
- C.R₁ / R₂
- D.R₂ / R₁
Correct Answer
(B) R₂² / R₁
Solution & Explanation
Answer: (b) Solution: Treat the large loop (R₁) as the source: its field at the centre is B = µ₀I/(2R₁), nearly uniform over the tiny inner loop (R₂). Flux through the small loop Φ = B·πR₂² = µ₀I·πR₂²/(2R₁), so M = Φ/I = µ₀πR₂²/(2R₁). Thus M ∝ R₂²/R₁. So the answer is B (R₂²/R₁).
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