GEOLOGY

Detailed explanation-1: -The current flows into the central part of the armature from the tail arm, which produces rotating torque with the magnetic field. In order to keep this direction of current, there should be some slots in the rear of the armature.

Detailed explanation-2: -As the armature current of a machine is typically much higher than the field current of a separately excited machine, the field winding in a series machine has fewer turns than the field winding in a separately excited machine. (Remember that mmf is the number of turns multiplied by current).

Detailed explanation-3: -A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine.

Detailed explanation-4: -When current flows through an armature winding, it generates a magnetic field which interacts with the magnetic field from the field windings to cause motor torque. Brushes and commutators are prone to wear. Permanent magnet motors are usually small-at most a few horsepower.