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Re: Transfering an Electrical Concept



Regarding where Brian W. wrote:
...
The maximum power theorem is well known to electrical engineers.
It may be expressed like this:
Maximal power is transfered when the source impedance equals
the characteristic impedance of the output.

At 08:32 12/20/00 -0500, David Bowman responded:

Actually, I think you will find that maximal power transfer for a
sinusoidal signal does *not* happen "when the source impedance equals the
characteristic impedance of the output". Rather, the impedance matching
condition for maximum power transfer is the condition where the load
impedance is the *complex conjugate* of the source impedence. This
means that the matched impedances for maximal power transfer are only
really equal when those impedances are purely resistive (i.e. real).
In order to get maximal power the reactance of the load needs to
cancel the reactance of the source so the current through the circuit
will be in phase with the voltage.

David Bowman
David_Bowman@georgetowncollege.edu


Quite so. The most famous example that comes to mind was the telephone
network that was proliferating at the end of the 1800's.
In order to increase the range of the phone wire, it was necessary
to load the line with series coils. This remedy for limited range seems
to have eluded the physicists initially, and to have rather been developed
by the 'electricians' of the day.

Brian

brian whatcott <inet@intellisys.net> Altus OK
Eureka!