Electromagnetic Induction

  • Electromagnetic induction is based on Faraday’s law, which states that a change in magnetic field within a closed loop of wire induces an electromotive force (e.m.f) in the wire.

  • This e.m.f production results in the flow of current within the wire if it is part of a complete circuit. The current thus produced is called the induced current.

  • Direction of induced current can be determined with Fleming’s Right Hand rule. If you stretch your thumb, forefinger and middle finger such that they are mutually perpendicular, with the thumb representing motion, forefinger representing the magnetic field and middle finger representing the current, they will show the directions of these quantities.

  • The amount of induced e.m.f is directly proportional to the rate of change of the magnetic field. If the magnetic field changes faster, the e.m.f production is greater.

  • The size of the induced current or voltage in a coil can be increased in several ways: by increasing the number of turns in the coil, by increasing the speed of the magnet, by using a stronger magnet, or by inserting an iron core into the coil.

  • Lenz’s law is closely related to electromagnetic induction and holds that the induced e.m.f will always work in such a direction to oppose the change that has produced it. This is a direct consequence of the conservation of energy.

  • The phenomenon of electromagnetic induction has many practical applications including in generators, transformers and induction cooktops.

  • Alternating current (AC) generators work on the principles of electromagnetic induction. As the coil or magnet within the generator spins, the magnetic field changes and induces an alternating e.m.f (and therefore an alternating current) in the coil.

  • Transformers, which are essential for transmitting electricity over long distances, also operate based on electromagnetic induction. Here, alternating current in one coil induces an e.m.f and hence current in a neighbouring coil.