Solenoid Through Coil A 17.0 cm long solenoid has 53 windings and a circular cross section of radius a = 1.70 cm. The solenoid goes through the center of a circular coil of wire with 24 windings and radius b = 8.50 cm. The current in the circular coil changes according to i(t) = 6.0 t2 + 1.0 t. What is the mutual inductance of the coil and solenoid? What is the magnitude of the emf induced in the solenoid at t = 3.50 seconds?