Question

(a) State Fleming's left hand rule.
(b) Write the principle of working of an electric motor.
(c) Explain the function of following parts of an electric motor :
(i) Armature (ii) Brushes (iii) Split ring.

Answer 1

(a) According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
(b) Principle of electric motor : When a coil carrying current is placed in a magnetic field, it will experience a force. As a result of this force, the coil begins to rotate.

(c) (i) Armature : It creates a magnetic field and the second role is to generate electromotive force.

(ii) Brushes : Carbon brushes are used to make contact with the rotating rings of the commutator and through them to supply current to the coil.

(iii) Split ring : Split rings are used to reverse the direction of current flowing through the coil every time the coil just passes the vertical position during a revolution.