A toroidal selenoid has 500 turns, cross-sectional area 6.25cm and mean radius 4.00cm
a) Calculate the coil's self inductance
b) If the current decreases uniformly from 5.00A to 2.00A in 3.00ms, calculate the selfinducee emf in th coil
c) The current is directed from terminal a of the coil to terminal b. Is the direction of the induced emf from a to b or from b to a ?