Question

Describe the principle, construction and working of an electric motor along with a figure.Answer the given question in detail.

Answer 1

$\bf{PRINCIPLE}$ : An Electric motor works on the principle of conversion of electrical energy into mechanical energy. $\textbf{\underline{The main point here to note and}}\\\textbf{\underline{keep in mind is that current}}\\\textbf{\underline{ has its own magnetic field.}}$

$\textbf{Construction of a sample small electric motor}$

•A loop SNMT of an insulated copper wire is placed in a permanent magnetic field such that part ST and NM of the wire is perpendicular to the applied magnetic field.

•The ends of this wire are connected to two semicircular rings A and B which are adjusted on an axle for their easy rotation.

•The outer part of the rings are connected to batteries by stationary brushes.

$\textbf{Working of a electric motor}$
When current is provided to the electric motor, the wire SNMT inside the motor get magnetised due to flow of current.
But the part SN and TM are parallel to the applied magnetic field so there will be no force acting on them, but the part ST and NM is perpendicular to the magnetic field hence a magnetic force acts on them and the part ST move upward. Now, the part SN is perpendicular to the magnetic field, so it move downward. Which complete one rotation of the wire SNMT. This goes on till there is current in the magnetic field.
The direction of movement is determined by $\bf{Fleming}$'s left-hand rule.