Question

(1) Draw a simple labelled diagram of a d.c. electric motor.
(2) What is the function of the split rings in a d.c. motor?
(3) State one advantage of a.c. over d.c.

Answer 1

Hint: d.c Is defined as direct current and a.c is defined as alternating current. A dc motor is based on the principle that a current-carrying conductor placed in a uniform magnetic field experiences a force. The direction of this force being given by Fleming's left-hand rule.

Complete step by step answer:
(1) A dc motor consists of the following components :

(a) Armature coil: It consists of a large number of turns of a rectangular Coil. ABCD is made of copper wire wound over a soft iron laminated core.
(b)Strong field magnets: Two poles of permanent magnets between which the armature coil is rotated.
(c) Split rings or half rings or commutator: The two ends of the coil are welded to two semi-circular metallic rings $R_1$ and $R_2$.
(d) Brushes: Two carbon brushes $B_1$ and $B_2$ make a contact with the split rings $R_1$ and $R_2$.

(2) The function of split rings: The function of the split rings is to change the direction of current flowing through the coil after each half rotation. The system of two half rings and the associated brushes are referred to as a split ring commutator.

(3) Advantage of a.c over d.c: when current is alternating the electric power can be transmitted over long distances without much loss of energy.

Note:
The speed of the motor depends upon:
(i) The strength of the magnetic field,
(ii) The current in the coil, and
(iii) The number of turns in the armature coil.