Two long coaxial solenoids, the primary P and the secondary S, are wound one over the other on the same cylindrical former. The arrangement is used in a laboratory demonstration of electromagnetic induction.
(i) Define mutual inductance between two coaxial solenoids.
(ii) State any three factors on which their mutual inductance depends and briefly explain the role of each factor.
(iii) The current in the primary is increased uniformly from 0 A to 5 A in 0.10 s. Using Lenz’s law, state the direction of the induced current in the secondary during this interval, assuming the current in the primary enters the near end of the solenoid. Justify your answer.