Experiments of Faraday and Henry – Class 12 | Chapter – 6 | Physics Short Notes Series PDF for NEET & JEE

Experiments of Faraday and Henry: Michael Faraday and William Henry were both experimentalists in the field of electromagnetism. Faraday is best known for his discovery of electromagnetic induction and the laws governing it, while Henry made significant contributions to the study of electrical resistance and inductance. Both scientists conducted a number of experiments, which led to their discoveries and helped establish the foundations of modern electrical and electronic technology. Some of Faraday’s notable experiments include his work on electromagnetic rotation and his discovery of the magneto-optical effect, while Henry is known for his work on self-induction and mutual induction, which helped to pave the way for the development of the telegraph and other electrical technologies.

Experiments of Faraday and Henry

Experiment 1:

In the first experiment of Faraday and Henry, a coil was connected to a galvanometer. Then a bar magnet was pushed towards the coil This was done in a way that the north pole was pointing towards the coil. It was noticed that as the bar magnet shifted, the galvanometer showcased deflection. The same thing was done with the South Pole.

It was observed in this experiment of Faraday and Henry that the shift and deflection took place only when the magnet was in motion and not when it was stationary. The point of deflection is small or large depending on the speed at which the motion takes place.

The conclusion of the Faraday and Henry experiment was that there was relative motion between the coil and magnet, resulting in the generation of current in the coil.

Experiment 2:

In the second experiment, Faraday replaced the bar magnet by a second current-carrying coil that was connected to a battery. Here, the current in the coil due to the connected battery produced a steady magnetic field, which made the system analogous to the previous one.

As we move the second coil towards the primary coil, the pointer in the galvanometer undergoes deflection, which indicates the presence of the electric current in the first coil. Similar to the above case, here too, the direction of the deflection of the pointer depends upon the direction of motion of the secondary coil towards or away from the primary coil. Also, the magnitude of deflection depends upon the speed with which the coil is moved. All these results show that the system in the second case is analogous to the system in the first experiment.

Experiment 3:

From the above two experiments, Faraday concluded that the relative motion between the magnet and the coil resulted in the current generation in the primary coil. However, another experiment by Faraday showed that relative motion between the coils was not necessary for the primary current to be generated. 

He used two stationary coils in this experiment, one connected to the galvanometer and the other to a battery via a push-button. The galvanometer in the other coil deflected as the button was pressed, showing the presence of current in that coil. Furthermore, the deflection in the pointer was only temporary; if the key was pinned down indefinitely, the pointer indicated no deflection, and when the key was released, the deflection reversed.

However, the third experiment of Faraday and Henry showcases that the relative motion is not necessary to produce current. Both of the coils are steadily placed, one is connected to the battery and the other to a galvanometer. The button in the battery when pushed repeatedly does not pass current but when pushed once, the galvanometer deflects.


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By Team Learning Mantras