×

# Faraday's Discovery of Electric Induction

Top
FAQ

## Introduction to Faraday's Discovery of Electric Induction

View Notes

The branch of physics that deals with the study of the electromagnetic force, which involves the interaction between the electrically charged particles are known as electromagnetism. Let us see who discovered electromagnetism? Electromagnetism was first discovered by William sturgeon. Electromagnetic induction or magnetic induction is the process through which the electromotive force is produced across an electric conductor in a changing magnetic field. Let us know ‘who discovered electromagnetic induction?’. It was discovered by Micheal Faraday in 1831 and it was mathematically described as Faraday’s law of induction by James Maxwell. The direction of this induced field was described by Lenz’s law.

Now we know who discovered electromagnetic induction, let us see how he invented it. Faraday demonstrated his experiment using an iron ring or torus, to which he wrapped the iron wires on the opposite sides. Depending on the understanding of the electromagnets he thought that when the current flows through a wire a kind of wave will start travelling through the ring, on the opposite side this wave will cause an electrical effect. He connected one end of the one wire to the galvanometer and the other end to the other wire to the battery, now he watched the fluctuations of the needle in the galvanometer. There he found a transient current and called it a Wave of electricity. This electricity was found when the wire is connected to the battery and then disconnected.

In Faraday's discovery of electric induction, due to the change in magnetic flux, this induction of electricity has occurred when the wire is connected to the battery and then disconnected. And with the span of two months, he observed several manifestations that are related to electromagnetic induction. One of them is as he saw the transient current when the bar magnet was slid in and out of the coil. By rotating the copper disk near the bar magnet with the help o a sliding electrical lead he generated a steady current also known as DC current.

Faraday electromagnetic theory was explained by using a concept which he called lines of force. As they were not formulated mathematically scientists who are present at that time rejected his theoretical work. But except a scientist called James Maxwell used Faraday's ideas as the basis of his electromagnetic theory. The time-varying aspect is expressed as the differential equation of the electromagnetic induction, this was referred to as Faraday’s law by Oliver Heaviside even though it was different from that of the original Faraday’s formulation and it has not described the motional EMF.

In the Faraday experiment, we have found how electric induction has occurred, now let us go through the laws he discovered.

Faraday’s law of induction and Lenz’s law: Faraday's law of induction uses magnetic flux through a region of space that is being enclosed by a wire loop. The magnetic flux used is defined by the surface area, Ф = $\int_{Σ}$ B. dA

In the equation given above “dA” indicates that the element of the surface Σ that can be enclosed by a wire loop. Whereas B indicates the magnetic field. The dot product of the magnetic field and the surface of the element indicates the infinitesimal amount of the magnetic flux produced. It can also be said that the magnetic flux through the wire loop is proportional to the number of magnetic flux lines that are passing through the loop.

Faraday’s law says that when the flux through the surface changes the wire loop acquires the EMF (Electromotive force). In a detailed way, we can tell that the EMF induced in the closed circuit is equal to the magnetic flux that is enclosed in the circuit.

ε = - $\frac{dФ_{B}}{dt}$

From the above equation, we can tell that is the EMF induced, ФB is the magnetic flux. Thus the direction of this EMF is given by Lenz’s law. It states that “The direction of flow of an induced current opposes the change that is produced by it”. Thus a negative sign is added to the equation. The generated EMF can be increased by exploiting the flux linkage by creating a tightly wound coil, this coil has N identical turns through which the same magnetic flux passes through it. Thus the resulting EMF is N times as that of the turns.

ε = - N $\frac{dФ_{B}}{dt}$

### Electromagnetic Force Discovery

In the world of physics Faraday and Maxwell, together, made great discoveries, the ones who discovered electromagnetic induction. Faraday with his experiments magnetic and electric fields are not telekinetic actions but they are the expression of physical things. With these experiments, Maxwell was inspired and he combined the ideas of all these results. The electromotive force produced across an electric conductor in a changing magnetic field is known as electromagnetic induction. The EMF is induced around the loop when the magnetic field through that wire varies.

### Applications

The Principle of Electromagnetic Induction is Used in Many Systems and Devices:

1. Electric Generator: The relative motion of the magnetic field and the circuit led to the generation of electric induction, this was discovered by Faraday this phenomenon is related to the electrical generators. When a permanent magnet moves in relation to the conductor or in vice versa an EMF is produced. The current flows through the wire that is connected to the electrical load thus electrical energy is generated by converting the mechanical energy into electrical energy.

The best example that suits this is the drum generator that is implemented using the idea of Faraday disc.

Here the rotating disc that is placed in the field of the uniform magnetic field that is perpendicular to the disc produces current that flows through the radial arm that is obtained by Lorentz force. To drive this current, mechanical work is required; a magnetic field is generated when this current flows through the conducting rim by the Ampere’s circuital law. Now the rim acts as an electromagnet that opposes or resists the rotating motion of the disc. Through the far sides of the rim, the return current flows from the rotating arm to the brush present at the bottom level. Current opposes the applied magnetic field resulting in the decrease of the flux at that side of the circuit. This opposes the flux that is increasing due to the rotation. The energy that is required to allow the disc in the motion despite that of the reactive force is equal to the electrical energy generated in the circuit. Thus this conversion of mechanical energy into electrical energy is found in all types of generators.

1. Electrical Transformer: The electrical current that flows through the loop of wire changes creates the changing magnetic field. The second wire that is in contact with the wire where the magnetic field is created experiences the change in the magnetic field. This is experienced as a change in the coupled magnetic flux. Thus the electromotive force formed in the second wire EMF is called induced EMF or transformer EMF. The flow of current can be observed when the two ends of these wires are connected to the electrical load. The best example of this is the Current clamp, it is a type of transformer that has a split core that can be clipped onto a coil or wire or it can be spread apart, this is done to calculate the current flowing through it or the current flowing in the reverse direction to the induced voltage. As per the conventional instruments it is not required to disconnect the clamp or it doesn’t make any electrical contact with respect to the conductor.

1. Magnetic Flow Meter: Faraday’s law is used to determine the flow of electric current in the conductors and slurries. These types of instruments are called magnetic flow meters. The induced voltage is generated in the presence of a magnetic field due to the conductive moving liquid at the velocity is given by:

ε = - Blv

Where is B is a magnetic field, ε is the voltage induced, v is the velocity and l is the distance between the electrodes that are present in the magnetic flow meter.

### Eddy Current

The electrical conductors that are moving through the steady magnetic field or the conductors that are stationary in nature are placed in changing magnetic fields; the circular currents induced in them are known as eddy currents. The eddy current flows through the closed loops in a plane that is perpendicular to that of the magnetic field. The eddy current is applied in the induction heating system and eddy current brakes. But the eddy currents that are induced in the metal magnetic cores of the AC motors and transformers are undesirable as they dissipate energy this is known as core losses. Thus to avoid core losses many methods are used: Instead of using the solid metal as the core, thus cores of low-frequency AC transformers and electromagnets. These are made of stacks of metal sheets known as laminations. The inductors and the conductors that are used for high frequency in these devices the magnetic core is made of non-conductive material that is magnetic in nature; they are iron powder or ferrite.

• When the solid metallic mass is rotated the eddy currents occur in the magnetic field due to the reason that more number of the magnetic field of lines passes the outer portion of the metal than that of the inner portion. Thus the EMF induced is not uniform.

• The eddy currents consume only a considerable amount of energy thus causing a rise in the temperature.

### Conclusion

The man who invented electromagnetic induction is Micheal Faraday. Where electromagnetic induction is the production of the EMF across a conductor that is conductive electrically in the presence of the magnetic field. The branch of physics which deals with the study of the EMF is known as electromagnetism. By the results that were produced in the Faraday, the experiment was used by Maxwell to invent more in the field of physics. This is the principle behind generators and electrical transformers that are being used today. These two devices play an important role in the production and regulation of electrical current.