Electric motors have huge range of applications in the modern world - Leaving Cert Physics - Question ii - 2016

When current flows through the coil of the d.c. motor, the following occurs:

1. Current Carrying Conductor in Magnetic Field: The coil acts as a current-carrying conductor placed in a magnetic field created by the surrounding magnet.

2. Force on Each Side: According to the Lorentz force law, the current flowing through the conductor experiences a force perpendicular to both the magnetic field and the direction of current. This causes the coil to experience forces on opposite sides.

3. Rotation: The net effect of the forces acting on either side of the coil generates a torque, causing the coil to rotate. This rotation is continuous due to the commutator's function of reversing the current direction, allowing sustained motion.

To demonstrate the principle of operation of an induction motor, you would need:

1. Apparatus: Set up an induction motor connected to an appropriate power supply.

2. Method: Start the motor and describe what happens when it is powered. You can show that the rotor spins without any physical connection to the power supply.

3. Observation: Note that the rotor turns due to electromagnetic induction—current induced in the rotor windings creates a magnetic field that interacts with the stator field, producing motion.

One significant advantage of an induction motor over a d.c. motor is that there is no sparking at brushes. This is because induction motors do not require brushes for their operation, leading to reduced maintenance and increased reliability.