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CONTENT 3

Applications of Magnetic Effect of an Electric Current

1. Electric bell

ELECTRIC BELL

The capacitor is used to reduce sparking effect at the contacts. The circuit is completed at the

contact spring and contact screw. 

Working Mechanism of an Electric Bell

  • When current is switched on, it flows through the circuit and the soft iron core becomes magnetized. The magnetized iron core then attracts the sot iron armature, which has a hammer at its end. On attraction, the hammer knocks the gong and the bell rings.
  • When the soft iron armature is attracted, the contact at the contact screw is broken and current stops flowing. The electromagnet loses its magnetism and releases the soft iron armature and this closes the contact again.This process is repeated and the bell rings continuously as long as the switch is closed.

2. Electric Motor.

  • It is a devise which converts electrical energy into rotational kinetic energy.
  • The permanent magnets are curved at the ends to produce radial magnetic field.

Functions of Carbon Brush

  1. Presses lightly against the commutators so that that the coil rotates freely and easily.
  2. Connect the coil to the electric current source.

Reasons why carbon brushes and commutators are made of graphite

  1. Graphite is a good conductor of electricity.
  2. It serves as a lubricant since it is slippery.

Working Mechanism of the Electric Motor

  • When the coil is horizontal and current passes through it as shown on the diagram, side AB experiences an upward force while BC experiences a downward force. The two forces make the coil rotate in the clockwise direction.
  • When the coil is in the vertical position with AB at the top and CD at the bottom, the brushes touch the spaces between the two split rings.
  • Due to momentum, the coil continues to rotate and the commutators interchange the contact positions with the brushes.
  • The current is then reversed in the coil and the forces acting on each side reverse in direction. Side AB is now on the right with a downward force while side CD is on the left with an upward force. The coil continues to rotate.
  • video tutorial on the motor


    • 3. Simple magnetic relay

magnetic relay

    • In a magnetic relay, one circuit is used to control another circuit without any dire
    • ct electrical connection between them.

    Working Mechanism of Magnetic Relay

  • When the switch is closed, current flows through circuit X; electromagnet is made on the solenoid and in turn attracts the soft iron armature. The closes the contacts in circuit Y.
  1. Circuit Breakers
  • Circuit breakers are used to protect electrical components from excessive flow of current.
  • 4. Moving coil speaker

 speakers                           coil speaker

A moving coil speaker converts electrical energy to mechanical sound energy.

video tutorial for moving coil speaker