All electrical machines have two sets of coils; one set (field coil in generator and motor and primary coil in transformer) produces the working magnetic flux φ, and the other set (armature coil in generator and motor and secondary coil in transformer) reacts to flux φ and produces an electromotive force (voltage) in the generator and transformer and a mechanical force (torque) in the motor. Both sets of coils are embedded in magnetic steel to produce the required flux with a minimum magnetizing (field excitation) current. The electromagnetic interaction between two sets of coils is governed by the following basic laws of physics.