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Two circular concentric loops of radii r 1 = 20   cm , r 2 = 30   cm are placed in the X - Y plane as shown in the figure. A current I = 7   A is flowing through them. The magnetic moment of this loop system is

Options

  1. A+ 0.4 k ^ A m 2
  2. B- 1.5 k ^ A m 2
  3. C+ 1.1 k ^ A m 2
  4. D+ 1.3 j ^ A m 2

Correct answer

C. + 1.1 k ^ A m 2

Step-by-step solution

Here, magnetic moment due to loop 1 M 1 = iA 1   = iπr 1 2   = 7 π 0 .20 2 = 0 .28 π Similarly magnetic moment due to loop- 2 M 2 = iA 2 = iπr 2 2   = 7 π   0 .30 2 = 0 .63 π Net magnetic moment   = M 1 - M 2   = 0 .63 π - 0 .28 π = 1 .1  A   m 2

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