Electromagnetic induction

ELECTROMAGNETIC INDUCTION

• Whenever the magnetic lines of force passing through a closed circuit change, a voltage and hence a current is induced in it. This phenomenon is called electromagnetic induction.
• Electromagnetic Induction was discovered by Michal Faraday in 1831.
• Either the conductor is placed in a moving magnetic field or a moving conductor is placed in a stationary magnetic field.
• The production of electricity form magnetism is called electromagnetic induction.
• The process of electromagnetic induction has led to the construction of generators for producing electricity at power stations.
• Applications: This discovery formed the basis of producing electrical energy in a circuit by using magnetic fields and not just batteries. Machines like motors, generators and transformers work on the principle of electromagnetic induction.

FARADAY AND HENRY’S OBSERVATION ABOUT ELECTRO MAGNETIC INDUCTION

• A current is induced in a coil when it is moved (or rotated) relative to a fixed magnet.
• A current is also induced in a fixed coil when a magnet is moved (or rotated) relative to the fixed coil.
• No current is induced in a coil when the coil magnets both are stationary relative to one another.
• When the direction of motion of coil (or magnet) is reversed, the direction of current induced in the coil also gets reversed.
• The magnitude of current induced in the coil can be increased:
  • By winding the coil on a soft iron core,
  • By increasing the number of turns in the coil,
  • By increasing the strength of magnet, and
  • By increasing the speed of rotation of coil (or magnet).

FACTORS RESULTING IN THE PRODUCTION OF VOLTAGE

Number of Coils: As the number of turn increases, the voltage induced in the coil increases. In other words, the induced voltage is directly proportional to the number of turns/coils of the wire.

Varying or changing magnetic field: By moving the magnetic field around the conductor or moving the conductor in the magnetic field, the induced voltage can be varied.

IMPORTANCE OF ELECTROMAGNETIC INDUCTION: FARADAY’S LAW

According to Faraday’s law of electromagnetic induction, the amount of voltage induced in a coil is proportional to the number of turns of the coil and the rate of changing magnetic field.

Mathematically, the induced voltage can be given by the following relation.

where,

e is the induced voltage (in volts)
N is the number of turns in the coil

FLEMING’S RIGHT-HAND RULE FOR THE DIRECTION OF INDUCED CURRENT

This rule gives the direction of the force exerted on a current carrying conductor placed in a magnetic field.

According to this rule if we hold the thumb, the forefinger and the central finger of the left-hand mutually perpendicular to each other and if the forefinger points in the direction of the magnetic field, central finger in the direction of the current, then the thumb points in the direction of motion (or the force) on the conductor.