Exercise 30.19 A solenoid 20.0 cm long and with a cross-sectional area of 0.570 cm2 contains 460 turns of wire and carries a current of 70.0 A. Part A Calculate the magnetic field in the solenoid. Part B Calculate the energy density in the magnetic field if the solenoid is filled with air. Part C Calculate the total energy contained in the coil's magnetic field (assume the field is uniform). Part D Calculate the inductance of the solenoid. L = H