A solenoid is 50 cm long, 2 cm in diameter, and contains 1500 turns. The cylindrical core has a diameter of 2 cm and a relative permeability of 75. This coil is coaxial with a second solenoid, also 50 cm long, but with a 3 cm diameter and 1200 turns. Calculate: L for the outer solenoid Please show steps to answer answer 192 mH Solution the inductance L of a solenoid is given by the equation. L= k*u 0 *N 2 *A/l it is given that the relative permeability of the given material is 75. length of the coil is 50 cms. the diameter of the solenoid is 3cms. so the radius is 1.5 cms. the solenoid is having 1200 turns. so, by susbtituting the given values we get L = 75*4*pi*10 -7 *pi*r 2 *1200*1200/0.5 =0.09593255477/0.5 =0.19186510955 H =191.8mH =192mH .