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JEE Mains · Physics · STD 12 - 5. Magnetism and matter

A magnet of total magnetic moment \({10\,^{ - 2}}\hat i\,A - {m^2}\) is placed in a time varying magnetic field, \(B\,\hat i\,\left( {\cos \,\omega t} \right)\) where \(B = 1\, Tesla\) and \(\omega  = 0.125\, rad/s\). The work done for reversing the direction of the magnetic moment at \(t = 1\, second\), is

  1. A \(0.01\,J\)
  2. B \(0.007\,J\)
  3. C \(0.028\,J\)
  4. D \(0.014\,J\)
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Answer & Solution

Correct Answer

(D) \(0.014\,J\)

Step-by-step Solution

Detailed explanation

Work done by external agent \( = {U_f} - {U_i}\) \(W=M B(1-\cos \Theta)\) \(W=2 M B \quad \quad M=10^{-2} \widehat{l}\, A-m^{2}\) \(=2 \times 10^{-2} \times 1 \times \cos (0.125) \quad B=B \widehat{l} \cos w t\)…
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