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Magnetic Induction Formula

Last updated date: 21st May 2024
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What Does the Magnetic Induction Formula Signify?

Magnetic induction is the phenomenon of the generation of electromotive force or e.m.f. in a conductor pertaining to the change in magnetic flux linked with it. It was discovered by the scientist Michael Faraday in 1831. Faraday’s law of induction was later mathematically represented by Maxwell. Magnetic induction is a very important scientific phenomenon and a crucial topic in physics. To understand what the magnetic induction formula signifies let us understand Faraday’s Law of Induction. Here we will also study the emf induced formula, faraday's law formula, and a few other important features of magnetic induction. 

Faraday's Law of Induction 

The magnetic field induction formula of Faraday states by a change in the magnetic flux linked to a conductor, an electromotive force (emf) is induced. The rate of change of the magnetic flux enclosed by a closed circuit is equal to that of emf.

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According to Faraday’s experiments 

ε is directly proportional to the change in flux 

ε is inversely proportional to Δt

ε produced in a coil having N turns is N times that of a single current-conduction coil (ε  ∝  N)

The magnetic flux passing through a surface of vector area A:

ΦB =B⋅A = BAcosθ

For a varying magnetic field the magnetic flux is B through an infinitesimal area dA:

dΦB = B⋅dA

The surface integral gives the total magnetic flux through the surface.

ΦB = ∫∫A B⋅dA

According to Faraday’s law formula, in a coil of wire with N turns, the emf induced formula in a closed circuit is given by

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

When flux changes by Δ in a time Δt.

The minus sign shows that a current I and magnetic field B opposite to the direction of change in flux is produced. This is known as Lenz’s law. 

Electromagnetic Induction Formula for Moving Conductor

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For a moving rod, N=1 and the flux Φ=BAcosθ, θ=0º and cosθ=1, a B is perpendicular to A. 

The area swept out by the rod is ΔA= lΔx

∴ ε = \[\frac{B \Delta A }{\Delta t}\] = \[\frac{Bl \Delta x}{\Delta t}\] = Blv

where v (velocity) is perpendicular to the B (magnetic field) 

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In the above scenario of a generator, the velocity is at an angle θ with B, so that its component perpendicular to B is vsinθ.

ε = Blv sinθ

Where, l = length of the conductor, 

v = velocity of the conductor 

θ = the angle between the magnetic field and the direction of motion.

Thus, the induced current formula signifies the close relationship between electric field and magnetic field which is dependent on a specific time variation.


The production of voltage (or EMF) over an electrical conductor placed inside a varying magnetic field is referred to as electromagnetic induction. The induced electromotive force in a closed circuit is equal to the rate of change of the magnetic flux enclosed by the circuit, according to Faraday's law.

FAQs on Magnetic Induction Formula

1. Determine the Magnetic Flux Formula in Terms of Current.

As the flux is produced in response to the current, the flux induced by a current is proportional to the current 

Thus, change in flux induces a current and a voltage which is proportional to the rate of change of flux. This is similar to Ohm's Law (V = IR). 

Thus we can say ΦB ∝ I

As we know  ΦB=B⋅A   

Where B = µ0NI

0 (permeability constant) = 4π10-7 T ]

Therefore, ΦB = µ0NIA

2. How to Establish an Inductor Energy Formula?

Energy is stored within a magnetic field of an inductor.

Due to energy conservation, the energy needed to drive the original current should have an escape route. In the case of an inductor, the magnetic field is the escape route of that current. The energy stored in an inductor is equal to the work needed to generate a current through the inductor. The formula for this energy is given as:

E =  \[\frac {1} {2}\]   LI2

where L is the inductance (unit - Henry) and I (Ampere).

3. How Electromagnetic Induction Is Used?

The devices that depend on electromagnetic induction: are electric generators and electric transformers. Both devices play important roles in producing and regulating the electric current we depend on in our daily lives.  Electric generators use electromagnetic induction to change kinetic energy to electrical energy. They produce electricity in power plants. Electric transformers use electromagnetic induction to change the voltage of the electric current. Some transformers increase voltage and others decrease voltage.

4. Explain electromagnetic induction in short?

Faraday's law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)—a phenomenon known as electromagnetic induction. It is the fundamental operating principle of transformers, inductors, and many types of electrical motors, generators, and solenoids.

5. How does magnetic induction work?

Induction (Electromagnetic Induction) is the production of current in a conductor as it moves through a magnetic field. A magnet produces lines of magnetic force, as seen in the graphic above. Iron filings align themselves along the invisible lines of flux. Due to Faraday's Law of Induction, if you take a wire and move it back and forth in a magnetic field, you cut across the lines of flux. The magnetic field pushes on electrons in the metal. Copper has 27 electrons; the last two in the orbit are easily pushed onto the next atom. This movement of electrons is electrical flow.