Re: Very basic question (Decrement (?) ...)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Cory Roussel by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <imcuddlycory-at-yahoo-dot-com>
> 
> Hello Coilers,
> 
> Here is a VERY basic question that has BOTHERED ME for
> a long time but i never really got to thinking about
> it too much... In a transformer, why is it that the
> poles are reversed on every cycle (IE AC)!?  Why is it
> necisary that the voltage be changed, and not
> constant...  I dunno these are very simple and i just
> cant figure out even though they are SO simple...

A wire transporting a current creates a magnetic field around it.
This works even with DC currents (Try with a small battery, a
wire, and a compass).
Many wires in parallel conducting the same current produce a
more intense field. This is why coils are used.

But: A magnetic field circulating around a wire only induces
a voltage on it if it is changing in intensity.

So, to make a transformer you make a coil where the current
is changing all the time (an AC current, for convenience),
that produces a varying magnetic field around it, and place
nearby another coil, that produces an AC voltage on its
terminals, induced by the varying magnetic field.

Antonio Carlos M. de Queiroz