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*From*: John Denker <jsd@av8n.com>*Date*: Fri, 23 May 2014 02:11:25 -0700

On 05/23/2014 01:38 AM, Savinainen Antti wrote:

http://www.bsharp.org/physics/transmission

What bothers me is that the loss fraction can conceivably be one or

even more, which is clearly not physical. Perhaps I am missing

something?

Starting from the formula

Ploss / P = P R / V²

= fractional loss

rewrite it as

Ploss / P = ΔV / V

which I find simpler to write, simpler to interpret, and in

all ways better.

So the fractional loss cannot be greater than unity ...

PROVIDED the load is passive.

To say the same thing the other way, you could have the

fractional loss exceed unity if the load is actively sucking

power out of the system. This *is* physically possible,

although I suppose it depends somewhat on what you define

as "the" voltage V and what you define as "the" load as

opposed to the source.

Higher-than-expected fractional loss is not even particularly

uncommon if you have a two-phase or three-phase AC power

distribution scheme, in situations where the symmetry is

broken by a higher-than-expected resistance in /one/ leg

of the distribution circuit.

Another common way this can happen is if you hook a

battery charger up to the battery /backwards/.

**References**:**[Phys-L] Power loss in transmission lines***From:*Savinainen Antti <antti.savinainen@kuopio.fi>

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