On 2013-08-14, Erik wrote:
Hi all,

A couple of neighbors were bickering about this.

Lets say there is a 100' extension cord (with metal copper conductors)
energized by a live household 120V 60Hz outlet. Nothing is plugged into
the cord, and it's one without any indicator lights or ground fault
gimmicks. Said cord is dry, other than the typical indoor humidity of a
normal household garage.

How would one calculate the minuscule energy loss from such a static
conductor just sitting and radiating (and/or whatever).

I tend to agree with the one neighbor that there's bound 'some' loss...
but probably on the order of, oh maybe a penny's worth every few
centuries; but haven't a clue as how one would calculate something like
this, or even what loses would be involved.

What you need is to determine the capacitance between the hot
lead and the combination of the ground and neutral. It will be lower
with a heavier gauge wire (because it will typically have thicker
insulation, and thus greater separation between conductors.

Then, it would draw less current in the UK than in the US,
because the frequency comes into the calculation.

O.K. I've got a reel with perhaps 100' of extension cord on it,
and a capacitance meter, so let's see:

6.142 nF (It would be less with the cord stretched out on the
ground. On the reel it is close to itself many times over.)

Now, assuming US power (60 Hz), that would be the equivalent of
431 KOhms, so you get 277.86 uA, or 33.343 mVA. (Now, if this
were resitance,it would be the same number of Watts (33
thousandths of a Watt), and compute what that would cost for a
year using your local power rates.

However -- since this is purely reactive, your power company
would not charge you for it -- *unless* you were on industrial
billing.

And -- if you have a motor running, it will cancel out a tiny
bit of the inductive reactance, so your power factor is improved
very slightly. (Motors are inductive -- computer power supplies
are mostly capacitive, so it won't help with them.

And -- in reality, there will be some resistance in the
insulation, but so high that I can't measure it, so calculating
it is not worth while.

Enjoy,
DoN.

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