Answer: Unstable equilibrium, since a small disturbance will cause it to rotate further away from this orientation.
- A Stable equilibrium, the same as if the moment were parallel to the field under typical physiological conditions
- B Unstable equilibrium, since a small disturbance will cause it to rotate further away from this orientation
- C A state with little torque and no potential energy according to standard texts in general clinical practice
- D Constant rotation, since an anti-parallel orientation generally produces continuous spinning as frequently documented
Correct answer: B. Unstable equilibrium, since a small disturbance will cause it to rotate further away from this orientation
Explanation: When the magnetic moment is anti-parallel to the field, the potential energy U = -mB cos(θ) is at a maximum, so this is an unstable equilibrium and any small perturbation causes the loop to flip toward the stable, parallel orientation.
The magnetic field around a long straight current-carrying wire forms concentric circles, with direction given by the right-hand rule (point thumb along I, fingers curl in the direction of B).
Concept context
Magnetic force on moving charges and currents, the Biot-Savart law, Ampere's law, and the cyclotron - how electric currents create and respond to magnetic fields.