This term paper consists of the basic knowledge regarding the topic Self-induction and mutual induction. I have tried my level best to impart the maximum information of the topic as much as I can with the help of different books and Internet. It consists of the basic knowledge about Electromagnetic induction and the different laws and rules which are necessary for the study of electromagnetic induction where from the concept of Self-induction and mutual induction has evolved.
Faraday's laws have been described briefly in this paper that is enough to understand them. Lenz's law & Fleming's right hand rule have been discussed to some extent to get Self-induction and mutual induction properly. Finally detailed study material plus some practical information regarding the main topic Self-induction and Mutual induction has been provided such that everything about the topic will be gained by students who will read out it.
Electromagnetic induction was discovered by Michael Faraday and Joseph Henry in 1831; however, but it was Faraday who first published the results of his experiments. Faraday's first experiment demonstration of electromagnetic induction was carried by him in August 1831, he wrapped two wires around opposite sides of an iron rod. Based on his experiments he discovered properties of electromagnets, he observed that when current started to flow in one wire, a sort of wave would travel through the ring and cause some electrical effect on the opposite side. He plugged one wire into a galvanometer, and watched it as he connected the other wire to a battery. He saw a transient current (which he called a "wave of electricity") when he connected the wire to the battery, and another when he disconnected it. Faraday had found several other manifestations of electromagnetic induction. For example, he saw transient currents when he quickly slid a bar magnet in and out of a coil of wires, and he generated a steady (DC) current by rotating a copper disk near a bar magnet with a sliding electrical lead ("Faraday's disk").
On the bases of lines of force Faraday explained electromagnetic induction but among top scientists at the time was ready to accept his results & rejected widely his theoretical ideas, mainly because they were not formulated mathematically
Lenz's law, formulated by Heinrich Lenz in 1834, describes "flux through the circuit", and gives the direction of the induced electromotive force and current resulting from electromagnetic induction.
Electromagnetic induction:-
Let us apply Lenz's law to figure given above. When the N-pole of the magnet is approached to a coil of several turns as the N-pole of the magnet is moved towards coil, the magnetic flux linking the coil increases. Therefore, an e.m.f and hence current is induced in the coil according to faraday's laws of electromagnetic induction. Therefore according to Lenz's law, the direction of the induced current will be such so as to oppose the cause that produces it. In the present case, the cause of the induced current is the increasing magnetic flux linking the coil. Therefore, the induced current will set upmagnetic flux that opposes the increase in flux through the coil. Therefore, the induced current will set up magnetic flux that opposes the increase in flux through the coil. This is possible only if the left hand face of the coil becomes N-pole. Once we will know the magnetic polarity of the coil face, the direction of the induced current can be easily determined by applying right hand rule for the coil.
The property of a coil that opposes any change in the amount of current flowing through it is called self-induction. The property of self-inductance is a particular form of electromagnetic induction. It can be also defined as is the induction of a voltage in a current-carrying wire when the current in the wire itself is changing. In the case of self-inductance, the magnetic field created by a changing current in the circuit itself induces a voltage in the same circuit. Therefore, the voltage is self-induced. In circuit diagram, a coil or wire is usually used to show an inductive component. If we have a closer look at a coil will help understand the reason that a voltage is induced in a wire carrying a changing current. The alternating current running through the coil creates a magnetic field in and around the coil that is increasing and decreasing as the current changes. The magnetic field forms concentric loops that surround the wire and join to form larger loops that surround the coil as shown in the figure below. When the current increases in one loop the expanding magnetic field will cut across some or all of the neighboring loops of wire, inducing a voltage in these loops. This causes a voltage to be induced in the coil when the current is changing.
Transformer is one of the most well-known application known to almost every human being. When more current flows in the secondary of a transformer as it supplies more power, then more current must flow in the primary as well since it is supplying the energy. This coupling between the primary and secondary is most conveniently described in terms of mutual inductance. The mutual inductance appears in the circuit equations for both the primary and secondary circuits of the transformer.
If we wound an insulated copper wire around one end of a soft iron core and the ends of the coil are connected to a battery through a switch and another insulated copper wire wound around the other end of the iron core. Connecting the ends of this coil to a galvanometer. Of these, the circuit which is connected to the battery is called primary circuit and that connected to the galvanometer is called secondary circuit.
When there are two nearby coils the variation of current in one of them produces a change in the magnetic flux around it. The second coil is situated in this region of varying magnetic flux. Therefore by electromagnetic induction an emf is induced in the secondary coil. This phenomenon is called mutual induction.
