Inductance – Mutual Inductance, Self Inductance, and Electric Induction

As we know magnetic fields are created around the electrically charged conductors, this process is known as electromagnetism. Electromagnetism deals with electrical fields as well as magnetic fields. When there is a steady or constant flow of the current in the conductor, a stationary magnetic field is produced. When there is an alternating or fluctuating current passed through the conductor, the magnitude or strength of the magnetic field also varies. When there is opposition to the change in the current that flows through the conductor, inductance is seen.

Inductance is the tendency of the conductor to oppose the flow of electric current. When there is a change in the flow of electric current, naturally there is an alteration in the magnetic field created. Changes in the magnetic field of the conductor induce a voltage known as ElectroMotive Force (EMF). The EMF created has the capacity to oppose the flow of current and is known as back EMF. The size of the induced EMF is directly proportional to the rate of change of the electric current in the conductor.

Back emf is given by the formula

Where,

• E is the induced back emf in volts
• L is the inductance of the coil in Henries.
• ΔI is the change in current, in amperes.
• Δt is the time taken for the change in current, in seconds.

The polarity induced by the back emf will be reversed compared with the changing voltage across the conductor, hence a negative sign is added in front of L.

What Is Inductance or Induction

Inductance is defined as the ratio of the induced voltage to the rate of change of current. Inductance is also known as Induction and is represented by the letter ‘L’. SI unit of inductance is Henry. Named after the great American scientist Joseph Henry, who discovered inductance.

1 Henry is defined as the amount of inductance required to produce an emf of 1 volt in a conductor when the current change in the conductor is at the rate of 1 Ampere per second.

An inductor basically features a wire wound around the core in the form of a coil. When current is passed through the inductor, it produces magnetic flux.

There are many factors that affect the inductance, they are:

• Number of turns of the wire in the inductor.
• Shape and size of the wire.
• The material of the core
• The shape of the core

There are two types of inductance:

• Self Induction
• Mutual Induction

Self Induction and Mutual Induction

When there is a change in the current in the coil, the magnetic flux in the coil also changes and results in an opposed induced electromotive force. This process is known as self-induction.

The current in the coil is directly proportional to the magnetic flux. Hence

Self induction is given by the formula

Where,

• L is the self inductance in Henries
• N is the number of turns
• Φ is the magnetic flux
• I is the current in amperes

When an emf is produced in a coil because of the change in current in a coupled coil (primary coil and secondary coil), the effect is called mutual inductance.

When there is a change in the current or magnetic flux linked with two coils, an opposing electromotive force is produced across each coil, and this phenomenon is known as mutual inductance. The induced current developed in the secondary coil opposes the growth of current in the primary coil, when the main current in the coil increases.

Mutual inductance is given by

Where,

• μ0 is the permeability of free space
• μr is the relative permeability
• N1 is the number of turns in coil 1
• N1 is the number of turns in coil 2
• A is the cross-sectional area
• l is the length of the coil in m

Hope you have understood about self inductance and mutual inductance. To know more about electric induction, visit BYJU’S – The Learning App.

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