Question 14.3: A circuit has 1000 turns enclosing a magnetic circuit 20cm^2 in section with 4A current, the flux density is 1 Wbm^-2 and with 9A current, it is 1.4Wbm^-2. Find the mean value of the inductance between these current limits and the induced e.m.f. If the current falls from 9A to 4A in 0.5s.