A solenoid of cylindrical geometry is shown in Figure P12.4.4.
(a) If the exciting coil carries a steady direct current I, derive an expression for the force on the plunger.
(b) For the numerical values I = 10 A,N = 500 turns, g = 5 mm, a = 20 mm, b = 2 mm, and l = 40 mm, find the magnitude of the force. Assume infinite permeability of the core and neglect leakage.
