Induced Electromotive Force and Current

What is an Induced Electromotive Force?

  • We can induce a current in the loop by changing the magnetic field. As we have discussed earlier in Faraday’s law, we have seen some experiments based on this theory.
  • In the first experiment, ammeter shows zero current reading which proves that a stationary magnet does not induce a current in a coil.
  • In the second experiment, the meter shows the induction of the current which demonstrates that it is due to the change in the magnetic field as the magnet is moved towards or away from the coil.
  • So it is clear that a constant magnetic field does nothing to the coil, while a changing field causes current to flow.
  • Hence we have observed from the above experiments that, only a changing magnetic field can make the current flow. To be more accurate, if the magnetic flux through a coil is changed, a voltage will be produced. This voltage is known as the induced emf.

What is Magnetic Flux?

  • Magnetic flux is linked with the surface area when it is held inside the magnetic field. When the direction ofmagnetic field is perpendicular to the surface area, magnetic flux on the surface is more. When the magnetic field is parallel to the surface area, magnetic flux on the surface is less.
  • Unit of magnetic flux is Weber (Wb).

Have you ever wondered; when the coil completely remains inside the magnetic field during motion, why no current flows through it?

When the coil is entirely inside the magnetic field, the two ends of the coil become positive and the other ends of the coil become negative. The potential difference of the coil will be equal in each case. So when two cells having equivalent electromotive force are connected to each other, then is no current flows through the coil and no net Induced Electromotive force exists in the coil.

Do you know what happens when the string of the electric guitar vibrates? When the string of an electric guitar vibrates, an electromotive force is introduced in the coil. The induced magnetization in the string is picked up from the vibration of the guitar. The input of an amplifier of the guitar is connected to the two ends of the coil which are connected to the speakers.