EMF Of Mutual Inductance

Michael Faraday in 1831 described scientifically the electromagnetic induction theory and also proposed Faraday’s law which helps in predicting the interaction of magnetic fields with the electrical circuit in order to generate an EMF (electromotive force). Faraday’s law of induction states that due to magnetic field changes a voltage or EMF in the conductor through circuit is induced and this is the process which is regarded as electromagnetic induction. This induced electromotive force opposes the change in current rate and is referred to as Lenz’s law. Inductance is mainly of 2 types and they are;

• Self-inductance
• Mutual Inductance

Mutual Inductance is the EMF (electromotive force) induced because the magnetic field of 1 coil or loop opposes voltage and current change in another loop which shows that both the coils are linked through magnetically because of change in the magnetic flux. The change in current rate of a coil is proportional directly to the EMF induced magnitude. The formula for mutual inductance is;

M= NΦ/I

where, M represents mutual inductance, N represents number of coils or loops, Φ represents magnetic flux and I represents the current induced. Kg.m².s-².A-² is the S.I. unit of it.

Electromagnetic induction or the magnetic induction is defined as the EMF or electromotive force production across the conductor (electrical) in the magnetic field. It is applicable in devices like transformers, inductors, generators, electric motors and many more.

EMF of Mutual Inductance

The EMF of Mutual Inductance is described by Faraday’s law and is always in the direction opposite to that of the magnetic field which is produced by the coil (coupled loop or coil). The self inductance induces the electromotive force (EMF) in the coil 1 while in coil 2, the EMF is caused by current change I1. Considering the 1st coil with turns N1, magnetic field B and current I1 while 2nd coil with turns N2 and current I2. Due to closeness of both the coils, some of the lines of magnetic field will also pass through the 2nd coil with the mutual inductance M21 which represents the mutual inductance of 2nd coil with regard to 1st coil. Φ21 will be the magnetic flux due to I1 in the second coil’s 1 turn.

The EMF of Mutual Inductance for 2nd coil can be represented by the formula;

EMF = -N2A (∆B/∆t) = -M (∆I1/∆t)

where, M represents proportionality constant between generated EMF in 2nd coil to current change in 1st coil

Applications of Electromotive force (EMF) of Mutual Inductance

The applications are as follows;

• Current clamp
• Induction welding
• Graphics tablet
• Induction motors
• Electric generators
• Inductive charging
• Digital signal processing
• Magnetic flow meters
• Transformers
• Induction sealing
• In stimulation of transcranial magnetic field (TMS- transcranial magnetic induction)
• Near field communications
• Flashlight which is mechanically powered
• In electrical devices
• Rowland rings
• In wireless transfer of energy
• In Eddy current’s calculation
• Induction cooking
• Inductors
• Hall effect meters

Factors Affecting the EMF of Mutual Inductance

The factors affecting the EMF of Mutual Inductance are as follows;

• The space available between two loops/ coils.
• Length
• Medium permeability
• Cross sectional area
• The number of turns for each coil.

Conclusion

Faraday’s law explained the concept of electromotive force (EMF) which is always opposite to the current rate and is produced by the electromagnetic induction across the conductor in presence of a magnetic field which changes continuously. It is useful in the designing and production of transformers, generators, induction cooking, flashlight and many more. The EMF of Mutual Inductance is affected by the cross sectional area, length, medium permeability, number of turns etc.