File Name: self induction and mutual induction .zip
When a steady current flows in one coil as in the left illustration, a magnetic field is produced in the other coil. But since that magnetic field is not changing, Faraday's law tells us that there will be no induced voltage in the secondary coil. But if the switch is opened to stop the current as in the middle illustration, there will be a change in magnetic field in the right hand coil and a voltage will be induced.
The self-inductance of a circuit is used to describe the reaction of the circuit to a changing current in the circuit, while the mutual inductance with respect to a second circuit describes the reaction to a changing current in the second circuit. If the two circuits are very far apart or if the field of one circuit provides no magnetic flux through the other circuit, the mutual inductance is zero. If the current is interrupted, as, for example, by opening a knife-blade switch, the current and therefore the magnetic flux through the coil drop quickly. Eddy currents are circulatory currents induced in the metal by the changing magnetic field. Unfortunately, reducing the heat loss increases the cost of transformers. Transformers used to transmit and distribute power are commonly 98 to 99 percent efficient. Eddy currents are induced in the object to be heated by surrounding a relatively nonconducting vacuum enclosure with a coil carrying a high-frequency alternating current.
Self inductance, L is a geometric quantity; it depends only on the dimensions of the solenoid, and the number of turns in the solenoid. Induction is also known as inductance. The relation is given as: Where M is termed as the mutual inductance of the two coils or the coefficient of the mutual inductance of the two coils. Consider a solenoid with turns which are wound on an iron core whose relative permeability is The self-induced emf present in the coil will resist the rise of current when the current increases and it will also resist the fall of current if the current decreases.
Electrical Principles II pp Cite as. When a current flows in a solenoid it establishes a magnetic flux. If the current changes in value, say, an increase, it causes the magnetic flux to increase. The converse of this is also true, and if the magnetic flux linking with a solenoid is altered, an e. This is the basis of electromagnetic induction. Unable to display preview.
Parametric description of appropriate line integral is used to determine the inductance per unit length by evaluating the vector potential integral along the edge of.
Under the effects of self inductance and changes in current induce an EMF or electro-motive force in that same wire or coil, producing what is often termed a back-EMF. As the effect is noticed in the same wire or coil that generated the magnetic field, the effect is known as self inductance. When current passes along a wire, and especially when it passes through a coil or inductor, a magnetic field is induced. This extends outwards from the wire or inductor and could couple with other circuits. However it also couples with the circuit from which it is set up.
So the induced current will oppose the primary current when the field is building. Conversely, when the field is collapsing the current will be in the opposite direction to try to prevent the collapse. In the first instance the induced current field will be in a sense to oppose the primary current building. In the second instance when the field is collapsing, it will be in the same direction to lessen the collapse.. The induced current is produced by a 'back EMF' - an induced voltage proportional to minus the rate of primary current change. Rearranging to make L the subject of the equation. Mutual induction concerns a pair of coils.
Definition: Self-inductance or in other words inductance of the coil is defined as the property of the coil due to which it opposes the change of current flowing through it. Inductance is attained by a coil due to the self-induced emf produced in the coil itself by changing the current flowing through it. If the current in the coil is increasing, the self-induced emf produced in the coil will oppose the rise of current, that means the direction of the induced emf is opposite to the applied voltage. If the current in the coil is decreasing, the emf induced in the coil is in such a direction as to oppose the fall of current; this means that the direction of the self-induced emf is same as that of the applied voltage. Self-inductance does not prevent the change of current, but it delays the change of current flowing through it. This property of the coil only opposes the changing current alternating current and does not affect the steady current that is direct current when flows through it. The unit of inductance is Henry H.
Physics pp Cite as. The electromagnetic phenomena we have discussed so far are those caused by currents which are unvarying in size and direction, resulting in steady magnetic fields. If the current is allowed to change in any way which causes a variation in the magnetic field with time, new phenomena appear which are classed under the heading of electromagnetic induction. These phenomena were first discovered by Faraday and shortly afterward, independently, by the American scientist Joseph Henry
Definition: Self-induced emf is the e. This phenomenon of self-induced emf can be further understood by the following example given below:. Consider a coil having N number of turns as shown in the above figure.
The apparatus used by Faraday to demonstrate that magnetic fields can create currents is illustrated in the following figure. When the switch is closed, a magnetic field is produced in the coil on the top part of the iron ring and transmitted or guided to the coil on the bottom part of the ring. The galvanometer is used to detect any current induced in a separate coil on the bottom.
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