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Post by abacus9900 on Feb 8, 2011 16:41:30 GMT 1
Inductors are very important components used in electronics circuits, but what are the principles underlying their operation? (Hope this question isn't too basic for Louise).
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Post by speakertoanimals on Feb 8, 2011 17:42:10 GMT 1
You run an electric current through a coil of wire. The current creates a magnetic field.
If you CHANGE the current, the magnetic field changes. Except a changing magnetic field through a coil (whether caused by the magnetic field generated by a current in a coil, or by moving a permanent magnet into the coil) generates a voltage (hence an electrical generator!). This voltage acts so as to oppose the change of current causing the changing magnetic field (else if it reinforced it, the whole thing would just sit there generating a bigger and bigger voltage all by itself!).
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Post by abacus9900 on Feb 8, 2011 17:51:56 GMT 1
Right. But what is the practical application in electronics?
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Post by principled on Feb 8, 2011 18:35:36 GMT 1
Hi Abacus
You probably already know this, but just in case...
All electronic ignition systems on petrol internal combustion engines use either inductive or capacitive systems to generate the high voltage (20kv+) necessary to produce the spark at the spark plug, which ignites the compressed charge.
The systems work on the principle that STA outlined.
If you want more detail about the system (which is pretty simple), please ask.
P
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Post by abacus9900 on Feb 8, 2011 19:59:53 GMT 1
Thanks principled. Well, I do know that coils (inductors) are used in electronic circuits to acts as 'chokes' which I gather 'filter' a narrow band of sinusoidal wave frequencies suitable for radio reception. How does that work?
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Post by speakertoanimals on Feb 8, 2011 20:32:15 GMT 1
The point about inductors is that they 'resist' changes in current (via the opposing voltage they generate), and the larger the change in current, the more resistance to that change.
SO, a steady current doesn't see the inductor. If I have an AC current of fixed amplitude, but variable frequency, the higher the frequency, the greater the rate of change of current, hence the greater 'resistance' of the inductor. Hence when I have a mixture of frequencies, the inductor tends to filter out the high frequencies, and smooth the current.
For radio, you need a tuned circuit, which is basically an inductance and a capacitor, which has a specfic resonant frequency. Think of connecting a charged capacitor to an inductor. The capacitor starts to discharge, but can't do that all at once, because the inductance resist abrupt changes in current. Hence we go from energy stored in the capacitor, to energy stored in the magnetic field of the inductor.
When the capacitor has no stroed charge left, the magnetic field in the inductor begins to decay, which starts current flowing again (magnetic field changing in a coil induces a voltage hence a current), until the magnetic field is all gone, and the capacitor is charged once again.
The exact time it takes to do this depends on the exact values of the inductance and capacitance, hence you can tune the circuit to the frequency you want.
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Post by abacus9900 on Feb 8, 2011 20:46:59 GMT 1
The point about inductors is that they 'resist' changes in current (via the opposing voltage they generate), and the larger the change in current, the more resistance to that change. SO, a steady current doesn't see the inductor. If I have an AC current of fixed amplitude, but variable frequency, the higher the frequency, the greater the rate of change of current, hence the greater 'resistance' of the inductor. Hence when I have a mixture of frequencies, the inductor tends to filter out the high frequencies, and smooth the current. For radio, you need a tuned circuit, which is basically an inductance and a capacitor, which has a specfic resonant frequency. Think of connecting a charged capacitor to an inductor. The capacitor starts to discharge, but can't do that all at once, because the inductance resist abrupt changes in current. Hence we go from energy stored in the capacitor, to energy stored in the magnetic field of the inductor. When the capacitor has no stroed charge left, the magnetic field in the inductor begins to decay, which starts current flowing again (magnetic field changing in a coil induces a voltage hence a current), until the magnetic field is all gone, and the capacitor is charged once again. The exact time it takes to do this depends on the exact values of the inductance and capacitance, hence you can tune the circuit to the frequency you want. Well, well, Jean I think I 'get it.' Nicely explained.  |
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Post by speakertoanimals on Feb 8, 2011 20:50:13 GMT 1
What's all this Jean crap?
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Post by abacus9900 on Feb 8, 2011 21:04:58 GMT 1
Thought that was your name. No?
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Post by Progenitor A on Feb 9, 2011 12:24:31 GMT 1
Thanks principled. Well, I do know that coils (inductors) are used in electronic circuits to acts as 'chokes' which I gather 'filter' a narrow band of sinusoidal wave frequencies suitable for radio reception. How does that work? One of the odd things about 'tuned circuits' with inductors and capacitors at resonance is that you get more volts out that you put in! And an odd thing abot capacitors is that you get current before you get voltage |
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Post by abacus9900 on Feb 9, 2011 12:41:03 GMT 1
How does that work naymissus? Yes, I seem to remember this.  |
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Post by Progenitor A on Feb 9, 2011 12:57:41 GMT 1
How does that work naymissus? Yes, I seem to remember this. I think Abacus, that you know far, far more than purport not to know, and ask these questios just in order to get a discusion going! Not that I object!  |
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Post by abacus9900 on Feb 9, 2011 16:10:04 GMT 1
Problem is, I've forgotten so much of it.  But seriously, do you not find it very satisfying to be able to communicate, in your own words, information to other people? If nothing else it's a good mental exercise and actually a challenge to convey ideas as clearly as possible. This is not as easy as some people might think, especially when trying to explain the 'basics' to a beginner. Think of the challenge an expert faces when writing a book for beginners about their area of expertise. |
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Post by speakertoanimals on Feb 9, 2011 16:51:45 GMT 1
Except what is the point if it is just done as some of test of our supposed teaching ability? There is little satisfaction to be had from trying to teach someone who already knows the answer, and is just pretending they don't! Which also shows rather bad form on the part of the original poster, if that is indeed the case. Isn't it just yet another wind-up, rather than a real discussion on a topic of interest?
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Post by abacus9900 on Feb 9, 2011 17:46:29 GMT 1
Except what is the point if it is just done as some of test of our supposed teaching ability? There is little satisfaction to be had from trying to teach someone who already knows the answer, and is just pretending they don't! Which also shows rather bad form on the part of the original poster, if that is indeed the case. Isn't it just yet another wind-up, rather than a real discussion on a topic of interest?  |
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