A precision laboratory resistor is made of a coil of wire. The coil is 1.25 cm in diameter, 4.5 cm long, and has 500 turns.

(a)What is its self-inductance in millihenries?

(b)What average emf in volts is induced if a 12.0 A current through it is turned on in 5.00 ms (one-fourth of a cycle for 50 Hz AC)?

(c)What is its inductance in millihenries if it is shortened to half its length and its 500 turns are counter-wound (wound as two oppositely-directed layers of 250 turns each)?