A conducting wire of length l is turned In the form of a circular coil and a current l is passed through it. For the torque, due to magnetic field produced at its centre, to be maximum, the number of turns in the coil will be
To maximize torque, the magnetic moment (m = nIA) should be maximized. For a
given length l, the area A is maximum when the number of turns n = 1, forming the
largest possible radius. Hence, the correct answer is (A) ONE.
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The torque (τ) on a current-carrying coil is given by:
τ = nI AB
For fixed wire length l, the radius is:
r = l/2πn
Torque is maximized when n = 2, as the product of the number of turns and area is optimized.
Answer: (B) Two
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