question_answer 25)

  An e.m.f. is produced in a coil, which is not connected to an external voltage source. This can be due to (a) the coil being in a time varying magnetic field (b) the coil moving in a time varying magnetic field (c) the coil moving in a constant magnetic field (d) the coil is stationary in external spatially varying magnetic field, which does not change with time

Answer:

  (a,b,c)An e.m.f. is produced in a coil without connecting it to an external voltage source only when amount of magnetic flux linked with the coil is changing with time. Choices (a) and (b) are correct Choice (c) will be correct when the coil is entering or leaving the constant magnetic field partially.