... and exactly what I said... the voltage drop is proportional to the
current flowing in the conductor.
The drop is twice for the same motor running at 110v/20A as for the
220V/10A. Again, the drop in the wire from the voltage source to the motor
is V=I * R. Twice the current, twice the voltage drop. It really is that
The thing I was taking issue with is the statement that "In other words, a
10A 220V cable will have
two hot wires, each of 10A 110V" Which is not really correct. If you had a
neutral and were using a device that references the neutral, then your
statement is correct. However, in the context of a 220 v service, there is
a 220 v potential across the two hots, not 2 sources of 110V. I was just
trying to be sure that anyone else looking at this thread does not get the
Ok. Truce. ;^}
Okay, ya got two 120v/100w bulbs wired in series, with 240v running through
them. Everything works properly; eventhough it is a 240v circuit.
Then you attach a neutral in between them. No current flows down the
neutral since the circuit is balanced, the lights don't change brightness;
everything is precisely the same as without the neutral. Everything works
properly; eventhough it is now a multiwire 120v circuit.
So, what does the neutral do? Nothing at all. There is 1.2a running
through each bulb with or without the neutral.
So what is the wrong impression?!
You picked a balanced condition. Just one of many posibilities. Do the
same with a 100w and a 60 w. The neutral will cary the imbalance. In fact,
if you measured carefully, you would find that in your scenario, that there
was a small current in the neutral. In the case of a 220v motor, which was
being discussed, there is no center tap. The windings are wired in series
for 220 and in parallel for 110. So what. In the absence of a neutral, you
have a 220v single phase feed. Period. You can try to call it two 110v
feeds, but you would be wrong. Add a neutral and you would then be correct.
There are so many misleading answers to electrical questions that it is best
to be precise and correct when providing information. Just because "you
could say that" does not make it technically correct.
As you stated. Two 110/120 legs is a common misconception, as is the
misconception that everything always has to be referenced to a grounded
conductor, or that there is something sacred about center-tapped transformer
I guess I should have said, "the % voltage drop is one quarter."
The voltage drop is one half, but it is figured into twice the voltage; so
the % drop is one quarter.
Since the actual voltage drop is irrelevant I was a tad sloppy; sorry.
I find it funny that you would criticize people for lack of information and
immediately follow it with wrong information!
What I think you are referring to is that there will be one quarter less
power wasted due to wiring resistances.
P = VI
I = V/R, V = IR
therefore, the power lost in wiring due to resistance in the wire is
When the current is cut by a factor of 2, the power lost is cut by a factor
of 2 squared, or 4.
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