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Thread starter mobinmk Start date Apr 29, Status Not open for further replies. Find a phase relation between current and voltage in an a. Why does the atmosphere change?
Why does a pure inductor pass DC and block AC of high frequency. Decay of current in inductor Problems on inductor.
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May I get a physical interpretation on this question? What is happening in the inductor when the current is running through it and what is physically happening when the current starts changing? In order to explain what is physically happening it might be helpful to consider the mechanical analogue of kinetic energy and the inertia of mass. The analogy is not exact, but it may hopefully give you a physical "feel" for what's going on, that is not so easy to feel with electrical concepts.
As niels nielson pointed out an inductor with a constant current produces a magnetic field. That magnetic field represents stored energy in the inductor, in this case, in the form of kinetic energy. A capacitor has stored energy in the electric field between the plates and, in that case, the stored energy is electrical potential energy.
Now think of a mass moving at constant velocity and having kinetic energy. It will resist any attempt to slow it down reduce its kinetic energy or speed it up increase its kinetic energy analogous to an inductor resisting any attempt to change its current and thereby changing the kinetic energy of its magnetic field.
The mass has inertia. The inertia to current change of an inductor is analogous to the inertia to velocity change of the mass. The analogy can be seen when one compares faradays law of induction. I would like to stress that inductance is not mass, velocity is not current, and voltage is not force. A one-farad capacitor holds a voltage across the plates of exactly one volt when it's charged with exactly one ampere per second of current.
Because inductors store the kinetic energy of moving electrons in the form of a magnetic field, they behave quite differently than resistors which simply dissipate energy in the form of heat in a circuit.
Energy storage in an inductor is a function of the amount of current through it. You can think of a magnet as a bundle of tiny magnets , called magnetic domains, that are jammed together. Each one reinforces the magnetic fields of the others. Each one has a tiny north and south pole. If you cut one in half , the newly cut faces will become the new north or south poles of the smaller pieces.
The average value of a whole sinusoidal waveform over one complete cycle is zero as the two halves cancel each other out, so the average value is taken over half a cycle. The average value of a sine wave of voltage or current is 0. That is, the flux linkage of the inductor with itself is changed.
Hence an EMF is induced inside the inductor , called as self induced emf. This self induced EMF will oppose its cause so its polarity is opposite to that of the source voltage , which is change in current. Hence an inductor opposes change in current.
So for a DC is concerned, inductor acts as an Magnet, hence its called as electromagnet. In AC, current is not constant.
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