A solenoid is to have an inductance of .272 mH, a cross-sectional area of 6.15x10^-4, and a length of 33.3 cm.
(a) How many turns per unit length should it have? turns/m
(b) If the self-induced emf is -11.2 mV at a given time, at what rate is the current changing at that instant? change in current/change in time.