An iron rod, characterized by an average permeability μ equal to 1850 times the permeability of free space μ₀, is the core around which two coils are wound. The first coil, with a length of 5 meters, consists of 400 turns, while the second coil has 180 turns. Each turn has a radius of 3 centimeters.

 

(a) Determine the mutual inductance between these two coils.

 

(b) If the current in the first coil decreases uniformly from 20 Amperes to zero over a period of 110 milliseconds, what will be the induced electromotive force (emf) in the second coil?