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NEET2026PhysicsChapterActual

A circular coil having magnetic moment is placed in a uniform magnetic field B . If the coil is in a state of unstable equilibrium, what is its magnetic potential energy?

Options

  1. A- B
  2. B+ B
  3. CZero
  4. D+ B 2

Correct answer

B. + B

Step-by-step solution

The magnetic potential energy of a magnetic dipole in a uniform magnetic field is given by U = - B = - B , where is the angle between the magnetic moment and the magnetic field B . For the coil to be in equilibrium, the net torque acting on it must be zero. The torque is given by = B , which implies = B = 0 . This gives = 0^ or = 180^ . In a state of unstable equilibrium, the potential energy is maximum. This occurs when = 180^ . Substituting = 180^ in the expression for potential energy: U = - B (180^ ) = - B (-1)

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