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JEE Mains · Physics · STD 12 - 4. Moving charges and magnetism

The magnetic moments associated with two closely wound circular coils \(A\) and \(B\) of radius \(r_A=10 cm\) and \(r_B=20 cm\) respectively are equal if: (Where \(N _A, I _{ A }\) and \(N _B, I _{ B }\) are number of turn and current of \(A\) and \(B\) respectively)

  1. A \(2 N _{ A } I _{ A }= N _{ B } I _{ B }\)
  2. B \(N _{ A }=2 N _{ B }\)
  3. C \(N _{ A } I _{ A }=4 N _{ B } I _{ B }\)
  4. D \(4 N _{ A } I _{ A }= N _{ B } I _{ B }\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(N _{ A } I _{ A }=4 N _{ B } I _{ B }\)

Step-by-step Solution

Detailed explanation

\(M = NIA\) \(M _{ A }= M _{ B }\) \(N _{ A } I _{ A } A _{ A }= N _{ B } I _{ B } A _{ B }\) \(N _{ A } I _{ A } \pi(0.1)^2= N _{ B } I _{ B } \pi(0.2)^2\) \(N _{ A } I _{ A }=4 N _{ B } I _{ B }\)
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