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Electromagnetic Induction

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Electromagnetic Induction, often known as induction, is a process in which a conductor is placed in a certain position and the magnetic field varies or remains stationary as the conductor moves. A voltage or EMF (Electromotive Force) is created across the electrical conductor as a result of this. Michael Faraday was credited for the discovery of electromagnetic induction in 1831 and he also gave the Law of Induction based on the experiments he performed. Independent of this discovery Joseph Henry also discovered a similar phenomenon in 1832.

What is Electromagnetic Induction?

Assume you go cashless when shopping and your parents utilize credit cards. The card is always scanned or swiped by the shopkeeper. The shopkeeper does not photograph or touch the card. However, he swipes/scans it. How does this swiping of the card remove money? This is due to a phenomenon known as ‘Electromagnetic Induction.’

Is it possible for moving things to generate electric currents? How can you tell whether there’s a connection between electricity and magnetism? Consider what life would be like if there were no computers, phones, or electricity. Faraday’s experiments resulted in the development of generators and transformers.

Electromagnetic induction

 

The induction of an electromotive force by the passage of a conductor through a magnetic field or by a change in magnetic flux in a magnetic field is known as electromagnetic induction.

This happens when a conductor is placed in a moving magnetic field or when it moves in a fixed magnetic field.

Michael Faraday discovered this electromagnetic induction rule. He put up a leading wire similar to the diagram above, which he linked to a device that measured the voltage across the circuit. The voltage in the circuit is measured when a bar magnet passes through the device. The significance of this is that it is a method of creating electrical energy in a circuit by employing magnetic fields rather than batteries. The principle of electromagnetic induction is used by devices such as generators, transformers, and motors.

Faraday law of Electromagnetic Induction

Faraday gave two laws of electromagnetic induction that are called the Faraday law of Electromagnetic Induction that are,

  • Faraday’s First Law of Electromagnetic Induction
  • Faraday’s Second Law of Electromagnetic Induction

Now let’s learn about these laws in detail.

Faraday’s First Law of Electromagnetic Induction

When a conductor is put in a changing magnetic field, an induced emf is produced, and if the conductor used is a closed conductor then, an induced current flows through it.

Faraday's First Law of Electromagnetic Induction

 

Faraday’s Second Law of Electromagnetic Induction

The magnitude of the induced EMF is equal to the flux change rate.

Faraday discovered that the induced emf in the coil depends on the various factor that includes,

  • Number of Turns in the Coils: The induced voltage is proportional to the number of turns/coils. The more turns there are, the more voltage is created.
  • Changing Magnetic Field: The induced voltage is affected by changes in the magnetic field. This can be accomplished by rotating the magnetic field around the conductor or by rotating the conductor inside the magnetic field.

Therefore, Faraday’s law of electromagnetic induction, states that 

“The amount of voltage generated in a coil is proportionate to the changing magnetic field and the number of turns of the coil.”

Lenz’s law of Electromagnetic Induction

Lenz’s Law states that when an emf induces according to Faraday’s law, the polarity (direction) of that induced emf opposes the cause of its creation.

According to Lenz’s law,

E = – N (dϕ ⁄ dt)

where,
E is the EMF produced
N is the number of tunrs of the coil
Negative Sign indicates that the induced emf opposes the cause of its production.

Learn more about, Lenz’s Law

Eddy Currents

Current loops induced in a conductor when placed in a changing magnetic field are called eddy currents. Eddy currents create a magnetic field that opposes the original magnetic field, which is similar to Lenz’s law. These currents are also called Foucault’s currents. Eddy currents have very useful applications such as metal detectors, electromagnetic braking, induction heating, etc.

Eddy Currents

 

Various applications of the Eddy Currents are,

Brakes of Trains: Breaking metal wheels on trains run on metallic tracks and when the brakes are applied, the trains’ metal wheels are exposed to a magnetic field, which induces eddy currents in the wheels. As a result of the magnetic interaction between the applied magnetic field and the eddy currents created in the wheels with friction-based braking, the trains slow down.

Induction Furnaces: The high temperature in the furnaces is prepared using the concept of eddy current.

Learn more about, Eddy Currents

Applications of Electromagnetic Induction

Some applications of Electromagnetic Induction are as follows:

  • Electromagnetic induction in AC generator
  • Electrical Transformers
  • Magnetic Flow Meter

Electromagnetic induction in AC generator

The production of alternating current is one of the most important applications of electromagnetic induction.

Electromagnetic induction in AC generator

 

More advanced equipment is the AC generator with a 100 MV output capacity. The effective area of the loop, when the coil spins in a magnetic field B, equals A cos θ, where θ is the angle between A and B. The principle of operation of a basic ac generator is this way of creating a flux change. The axis of the rotating coil is perpendicular to the magnetic field direction. The magnetic flux across the coil changes as the coil rotates, causing an emf to induct in the coil.

Electrical Transformers

An electrical transformer is another major use of electromagnetic induction. A transformer is a device that uses a magnetic field to convert ac electric power from one voltage level to another. The voltage in the primary of a step-down transformer is higher than the voltage in the secondary. A step-up transformer is one in which the secondary voltage has additional turns. To increase the voltage to 100 kV, power providers employ a step transformer, which decreases current and reduces power loss in transmission lines. Household circuits, on the other hand, employ step-down transformers to reduce the voltage to 120 or 240 V.

Electrical Transformers

 

Magnetic Flow Meter

Magnetic Flow Meter or Electromagnetic Flow Meter is the device used to measure the velocity or volumetric flow of fluids and uses the principle of electromagnetic induction to do so. Magmeter (commonly used term for Magnetic Flow Meter) can only measure the flow of conductive fluids.

Read More,

Solved Examples on Electromagnetic Induction

Example 1: When a bar magnet is placed near to the circular coil having 50 turns, the magnetic field density changes at a rate of 0.10 T ⁄ s. Find the emf induced in the coil.

Solution:

Number of turns, N = 50 turns

Rate of change of magnetic flux, dϕ ⁄ dt = 0.10 T ⁄ s

E = – N (dϕ ⁄ dt)

⇒ E = – 50 × 0.10 V

⇒ E = – 5 V

Hence, the emf induced in the coil is 5 V.

Example 2: A loop of wire is placed in a magnetic field and the magnetic flux through the loop is increasing at a rate of 0.02 T·m²/s. if the resistance of the loop of wire is 5 ohms then what is the induced current in the loop?

Solution:

For a loop of wire, N=1, and the rate of flux increase is 0.02 Tm2/s i.e., dϕ ⁄ dt = 0.02 Tm2/s

resistance of loop of wire is 5 ohm,

According to Lenz’s Law, E = -N(dϕ ⁄ dt)

E = -1×(0.02) = 0.02 Volts

We know Ohm’s Law  states, V = IR

⇒ I = V/R = 0.02/5 = 0.004 Ampere = 4 Mili Ampere

Thus, the Induced current in the wire loop is 4 mili ampere.

FAQs on Electromagnetic Induction

Q1: What is Electromagnetic Induction?

Answer:

Electromagnetic Induction is the induction of an electromotive force by the motion of a conductor through a magnetic field or by a change in magnetic flux in a magnetic field.

Q2: What is Faraday’s Law of Electromagnetic Induction?

Answer:

Faraday’s law of electromagnetic induction, states that the amount of voltage generated in a coil is proportionate to the number of turns and the changing magnetic field of the coil.

Q3: What is Lenz’s Law?

Answer:

According to Lenz’s law, the induced emf opposes the cause of its production,i.e., E = – N (dϕ ⁄ dt). The negative sign indicates that the induced emf opposes the cause of its production.

Q4: What are applications of Electromagnetic Induction?

Answer:

Various applications of electromagnetic induction are,

  • Electromagnetic induction in AC generator
  • Electrical Transformers
  • Magnetic Flow Meter


Last Updated : 14 Jun, 2023
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