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If we take any charged coil, it will have both an electric current flowing through it, as well as a magnetic field around it. This magnetic field opposes the flow of current in the coil, and following Faraday’s Law, creates an emf or electromotive force in the coil. The coil basically has a voltage across it. This process is known as induction and the measure of inductance is known as inductance.
We can also define inductance to be the ratio of the rate of change of current flowing through the coil or conductor. It is affected by the shape of the conductor, its material, as well as surrounding magnetic fields. The rate of current flowing through the conductor also contributes to the inductance. Usually a helix or wire or a coil is used if the induced emf or voltage is to be used for any purpose.
What is Mutual Inductance?
When you bring two charged coils near each other, their magnetic fields will act in opposite directions. The emf induced due to the magnetic field will oppose the current flow and voltage in another coil. This process where the magnetic field of one charged coil affects the current and voltage of a secondary coil is known as mutual inductance.
Mutual Inductance Formula
Mutual inductance can be represented using a very simple formula. The mutual inductance formula is:
Here, M is the mutual inductance.
0 is the permeability of free space and 0=410-7 N/A². N/A² stands for newtons per ampere squared and the unit of permeability of free space.
is the permeability of air. If some material is placed between the coils, then becomes the permeability of that material.
N1 is the number of turns in the primary coil.
N2 is the number of turns in the secondary coil.
A represents the area of the cross section of the coils.
l is the length of the coil
The SI unit of mutual inductance is henry and it is represented using H.
Reciprocity Theorem
Several experiments and studies done regarding the concept of mutual induction shows that the process follows the reciprocity theorem. This means that the value of mutual inductance on the second coil due to the first is the same as the value of mutual inductance on the first coil due to the second.
So, we can say, M12=M21=M
However, this property is only valid if there is no material medium between the charged coils in consideration. The theory of reciprocity becomes invalid in such a case as the material medium affects the magnetic field and hence the mutual inductance.
Conclusion
This article must have helped you understand the basics of mutual inductance. You can surely guess and estimate how important mutual inductance is in Physics. It is extremely important in many applications of electronics for home and industry use. You can get a better understanding of the concept by solving related problems. The proper practice would help you solve mutual inductance problems and questions in many exams.
