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Question about DC and AC current as it relates to circuts.

 
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Lock-Os
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Joined: 15 Oct 2008
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Location: Pittsburgh, PA

PostPosted: Wed Nov 19, 2008 10:12 am    Post subject: Question about DC and AC current as it relates to circuts. Reply with quote

Okay, I know that DC is basically a current going around in a straight path consistently, and that AC is current going back and forth over a period of time.

Now, my question is what kind of circuits use what kind of current and why?

So far, I can see why a computer might use DC since the flow of electrons kinda needs to be in one direction to transfer information correctly. Other than that, what would be the reason to use either one for certain circuits?
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Tekwiz
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Joined: 20 Oct 2008
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Location: Vancouver Island

PostPosted: Wed Nov 19, 2008 2:44 pm    Post subject: Reply with quote

Boy, talk about a tough question. It's like asking how high is up. One could write many thousands of words, yet still not give the entire answer. However, one of the main reasons for the use of AC is that only AC can be transformed through a transformer. This has major implications for power transmission, & motors of all kinds. AC motors are much simpler & cheaper than DC motors, because the alternating current can easily be made to produce a rotating magnetic field, without the use of commutators or expensive switching techniques. This is the major reason why all mains power supplies are AC, rather than DC.
Another reason is that signals or information must be AC in nature, because a smooth even flow of electrons won't tell you much.
I am sure others will elaborate on this, but these are two of the main reasons why AC is used.
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Alan
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PostPosted: Wed Nov 19, 2008 9:01 pm    Post subject: Re: Question about DC and AC current as it relates to circut Reply with quote

Lock-Os wrote:
Okay, I know that DC is basically a current going around in a straight path consistently, and that AC is current going back and forth over a period of time.

Now, my question is what kind of circuits use what kind of current and why?

So far, I can see why a computer might use DC since the flow of electrons kinda needs to be in one direction to transfer information correctly. Other than that, what would be the reason to use either one for certain circuits?


As Tekwiz mentioned this is a big topic. I have found a few Wikipedia articles that describe it quite well.
http://en.wikipedia.org/wiki/Direct_current
http://en.wikipedia.org/wiki/Alternating_current
http://en.wikipedia.org/wiki/AC/DC_(electricity)

Many items can operate from both AC and DC current. An incandescent light bulb for instance, the filament glows bright when current is flowing though it and it will light equally bright regardless of the direction of current.

Other devices will only operate with DC current, an LED for instance needs current to flow in a single direction for it to light. A battery stores energy and is also DC by nature.

Audio that is played into a speaker is AC so that the speaker cone can be forced back and forth (a speaker is basically a electromagnet connected to a cone). Much of the circuitry within a stereo manipulate AC waves which represents the sound we eventually hear.

You might want to pick up a book http://www.amazon.com/s/ref=nb_ss_b?url=search-alias%3Dstripbooks&field-keywords=ac+dc+fundamentals&x=0&y=0

You can get one from the library or in a used book store, don't worry about how old it is since the basics haven't changed any time recently. Smile
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