A simple induction motor consists of a metal cage placed inside three coils of wire.
As we apply an alternating voltage to the three coils,
the metal cage experiences a force, causing it to rotate.
To understand how and why an induction motor works,
we only need to know two facts about electromagnetism.
The first fact is that particles with the same charge moving in the same direction
exert an attractive magnetic force on one another…
and that particles with the same charge moving in opposite directions
exert a repulsive magnetic force on one another.
The second fact is that all moving charged particles create magnetic fields,
and that magnetic fields do not like to change.
Whenever we try to change a magnetic field, it will create an electric field which
will try to move charged particles in such a way so as to cancel out this change.
The moving charged particles in each of the three coils
create magnetic fields as is shown.
These three magnetic fields add together to produce
a total magnetic field that is rotating in space.
The effect of this rotating magnetic field is the same as it would be if it
was produced by just a single rotating ring of moving charged particles.
To understand the effect of this rotating magnetic field on the metal cage,
let us first consider just one loop of the metal cage,
which we can think of as a metal ring.
As the magnetic field rotates, the strength of the
magnetic field flowing through the loop is constantly changing.
Magnetic fields do not like to change.
If we have two rings of charged particles, and we try to
reduce the magnetic field through the loops by stopping
the rotating ring, the stationary ring will then start to rotate
in the same direction as the first, so as to try to keep the
magnetic field through the loop constant.
If we try to increase the magnetic field through the loops
by increasing the rotation of one of the rings, then the
other ring will react by rotating in the opposite direction so
as to cancel out this increase, and so as to again try to keep
the magnetic field through the loop constant.
As the moving ring rotates towards the metal loop, the
strength of the magnetic field through the metal loop increases.
As the rotating ring of charged particles rotates away from the metal ring,
the strength of the magnetic field through the metal loop decreases.
As the moving ring rotates towards the metal loop,
the strength of the magnetic field through the metal loop increases.
The metal loop consists of charged particles that are able to move through the metal.
As the rotating ring rotates away from the metal loop,
the strength of the magnetic field through the metal loop decreases,
causing the charged particles in the metal loop to move
in the same direction as the charged particles in the rotating ring,
so as to keep the magnetic field constant.
As the rotating ring rotates towards the metal loop,
the strength of the magnetic field through the metal loop increases,
causing the charged particles to move in the opposite direction of the charged
particles in the rotating ring, so as to keep the magnetic field constant.
As the rotating ring rotates away from the metal ring,
the charged particles in the metal ring move in the
same direction as the charged particles in the rotating ring.
Particles with the same charge moving in the same direction
create an attractive magnetic force on one another.
As the rotating ring rotates towards from the metal ring,
the charged particles in the metal ring move in the
opposite direction as the charged particles in the rotating ring.
Particles with the same charge moving in opposite
directions exert a repulsive magnetic force on one another.
As the rotating ring rotates away from the metal ring,
the charged particles in the metal ring move in the
same direction as the charged particles in the rotating ring.
Particles with the same charge moving in the same direction
create an attractive magnetic force on one another.
In both cases, the metal ring feels a force causing it to
rotate in the same direction as the rotation of the magnetic field.
This is true for all the metal loops that make up the metal cage,
and this is what causes the metal cage to rotate.
Much more information about electromagnetism and its applications
is available in the other videos on this channel.