State the principle of conservation of energy - Leaving Cert Physics - Question 10 (b) - 2007

In an electric motor, the main energy conversion is from electrical energy to mechanical energy. The input electrical energy facilitates movement, resulting in mechanical work.

(i) The commutator serves to reverse the direction of current through the coil in the motor at every half cycle, ensuring continuous rotation.

(ii) The carbon brushes connect the external power supply to the commutator to enable current to flow into the rotating coil as it turns.

(iii) The magnet provides a magnetic field that interacts with the current-carrying coil, enhancing torque and facilitating movement.

The motor turns because the coil carries an electric current, creating a magnetic field around it. This magnetic field interacts with the external magnetic field of the motor, resulting in a force that causes the coil to rotate. The phenomenon follows the Lorentz force law, where a current-carrying conductor experiences a force in a magnetic field.

One significant advantage of an induction motor over a DC motor is that induction motors have no brushes, which leads to less maintenance and enhanced reliability due to reduced wear and tear.

Apparatus: An aluminum disc, a magnet.

Arrangement: Place the disc on a pointed pivot.

Procedure: Rotate the magnet near the disc, which induces a current in the disc due to the changing magnetic field. This current then creates its own magnetic field that interacts with the magnet's field, causing the disc to rotate.

Observation: The disc rotates in the same direction as the magnet is moved, demonstrating the principle of electromagnetic induction.