What is induced voltage?

An induced voltage is called electric potential created by the effect of a changing electromagnetic field on a conductive material. The discovery of this phenomenon, known as electromagnetic inductionis attributed to Michael Faradaywho published the first results of his experiments in 1931. It was also independently discovered by joseph henry in 1932.

One of Faraday's experiments, which can be seen in the image below, consists of two coils of wire, one inside the other but not touching. The internal coil connects to a battery. And the external coil to an instrument that allows detecting electric current, Faraday used a galvanometer.

The battery generates a current that reaches the internal coil and creates a magnetic field. While it remains static, there is no electrical current in the external coil and the galvanometer detects nothing. But by moving the inner coil, in and out of the outer coil, changes in the magnetic field induce an electric current in the external coil.

Faraday's Law

Faraday's Law explains electromagnetic induction using magnetic flux. According to this law, by changing the magnetic flux of a conducting surface, an electromotive force is created. In the most widespread version, applied to closed circuits, this electromotive force is equal to the rate of change of the electromagnetic flux:

Faraday's Law


  • ε is the electromotive force
  • ΦB. is the magnetic flux

The formula for Faraday's Law has a negative sign following the Lenz's Lawaccording to which, the direction of the generated current is opposite to the direction of the magnetic field strength that creates it.


One of the most common applications of induced voltage is dynamos and Electric generators. These devices rely on the movement of a permanent magnet relative to a conductive material, or vice versa, to create an electrical potential or voltage. If the conductor is connected to an electrically consuming component (load), current will flow.

The same principle of current flow is applied in many types of devices, such as amperometric sensors, induction motors, electrical transformers, or induction cookers. In the field of health, electromagnetic induction is used in transcranial magnetic stimulation.

Electromagnetic induction can also be a problem. For example, electrical discharges that occur with lightning can induce voltage changes in high-voltage towers and cause problems in electrical networks that mainly affect sensitive electronic devices.

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