Electromagnetic Induction

Overview

Magnetism has a magical charm about itself. Its ability to affect metals like iron, cobalt, and nickel on touching them captivates the children's imagination. By witnessing the shape of the magnetic field formed by the iron filling surrounding the bar magnet, we can learn about the repulsion and attraction between the magnetic poles. The forces governing both the magnetism and electricity are much stronger than the gravity as per physicists regarding electromagnetism. The perfect example of this power is the maglev train suspension above its tracks.

What is Electromagnetic Induction?

Electromagnetic induction is the production of electromotive force otherwise known as voltage across an electrical conductor where the magnetic field changes. For the discovery of induction, Micheal Faraday was awarded this credit in 1831. Here, the Faraday’s law of induction was described by Maxwell in mathematical terms.

Take for example any conductor and place it in a specific position. Here the process of electromagnetic induction will let the conductor vary keeping the magnetic field stationary.

Now, there is a simple question to ask. Without touching another circuit, how is current induced by another circuit? Further, what does any of this have to do with magnetism? Before learning about that, we need to look at a few principles linking electricity and magnetism:

  1. The magnetic field surrounds every electric current.

  2. Fluctuating magnetic fields created around alternating currents.

  3. Faraday's Law states that the magnetic field causes the flow of the current in conductors that are placed within them.

Principle of Electromagnetic Induction

When we combine these above mentioned three principles, it means that a changing electric current is surrounded by a related changing magnetic field, which will, in turn, generate an electrical current in a conductor placed within it, having its magnetic field. It is the electromagnetic likeness of nesting Matryoshka dolls. The first current generated the second current in electromagnetic induction when a current flows through a conductor placed in a magnetic field.

When it comes to the principle of electromagnetic induction, it will enable the transformers, motors, electric generators and other rechargeable items such as wireless communication devices or electric toothbrushes to adopt the principle. Apart from that, your rice cooker works on using induction. Now let's learn how induction cooktops are heated by using induced current.

The Electromagnetic Induction Diagram is Shown Below:

Faraday's Law is the equation that mathematically describes the electromagnetic induction. It states that voltage (EMF) will be induced when there is a change in the magnetic environment of a coiled wire. Many ways were discovered by Faraday for this to happen. For example: by changing the magnetic field strength by moving a magnet over a coil of wire or by moving a coil of wire through a magnetic field, etc. The voltage (EMF) generated can be explained by the help of the following equation: 


 \[EMF = -N\frac{\Delta (BA)}{\Delta t}\]

Where:

N is the number of turns in the wire.

Δ(BA) is the difference in magnetic flux. 

Δt is the difference in time. 

Faraday's methods found the change in flux and can be expressed with the help of this equation. But because of Lenz's Law, this equation is negative, as it requires the change in magnetic flux to be reproduced in equal strength and the opposite direction by the wire.

For many electromagnetic applications around the world, including cars, Faraday's Law is important. For example, in a car the ignition system, the internal combustion engine takes only 12 volts from the battery and ramps it up to 40000 volts.

The use of magnetic flux through a wire is stated by the Faraday's Law of electromagnetic induction. The magnetic flux is defined as:

   \[\phi _{B} = \int _{\sum }B.dA\]

Here ΦB is the magnetic flux

dA is the surface of the element

B is the magnetic field. 

According to Faraday's Law of induction, when there is a change in the flux through the surface, the wire coil obtains the electromagnetic force. The rate of variation in magnetic flux, which is surrounded by the circuit, is equal to the induced electromotive force in a closed circuit as per the Law. 

  \[\epsilon = -\frac{d\phi_{B}}{dt}\]

Here\[\epsilon\]  is EMF

ΦB is the magnetic flux

t is the time. 

With the help of Lenz's Law, the direction of the electromotive force given. It states that when an electric current is induced by changing the magnetic field of a source, it will always create a counterforce opposing the force induced in it.

The Law explains such phenomena as diamagnetism and the electrical properties of inductors. 

\[\epsilon = -N\frac{d\phi_{B}}{dt}\] 

With the help of variation in magnetic flux through the surface of a wire loop, an EMF can be generated.

  • The magnetic field B variations.

  • The wire loop is misshapen, and the surface Σ changes.

  • The alignment of the surface dA changes

FAQ (Frequently Asked Questions)

1. What are the Uses of Electromagnetic Induction?

Ans In a changing magnetic field, an electromotive force will occur in an electric conductor, i.e., either (1) the motion is relative to a magnet or (2) the changing electric current produces changes in the magnetic field. For example, because of electromagnetic induction, an electric generator produces current.

There is other equipment from washing machines to trains, electric hobs, cookers, welding, guitar pickups, and transformers, which uses electromagnetic induction with the help of the electric motors.

For example, in Gill R&D, electromagnetic induction is used for non-contact position sensors. The electromagnets induce an eddy current in the sensor into the moving actuator, which in turn generates their magnetic field. Here, the eddy current generates resistive loss that converts some forms of energy like kinetic energy to heat. 

With the help of the multiple sensors along the surface of the multiple coils, the strength of the induced magnetic field traveling along the direction can be determined. In the sensors, the electronics are integrated to detect the field accurately and determine the position of the activator relative to the sensor.

The Gill R&D vast experience in the application of induction technology in the wide variety of the products and devices enables the delivery of innovative and creative solutions to customers' needs.

Electromagnetic Induction is also used in the following devices:

Current clamp, Electric generators, Electromagnetic forming, Graphics tablet, Hall effect meters, Induction cooking, Induction motors, Induction sealing, Induction welding, Inductive charging, Inductors, Magnetic flow meters, Mechanically powered flashlight, Pickups, Rowland ring, Transcranial magnetic stimulation, Transformers, Wireless energy transfer.


2. What are the Applications of Electromagnetic Induction?

Some essential electromagnetic induction applications  are:

  1. Electromagnetic induction in AC generator

  2. Electrical Transformers

  3. Magnetic Flow Meter