question_answer 42)

  Three identical bar magnets are rivetted    together at centre in the same plane as shown   in Fig. 3(EP).15. This system is placed at rest      in a slowly varying magnetic field. It is found       that the system of magnets does not show any motion. The north-south poles of one magnet is shown in the Fig. 3(EP).15. Determine the poles of the remaining two. 

Answer:

                    The system will be in stable equilibrium if the          net force on the system is zero and net torque on the system is also zero. It will be so if the poles of the remaining two magnets are as shown in Fig. 3(EP).16.