# How is this possible? What is voltage? 7.2 KV going through this small wire?

#### foolios

Joined Feb 4, 2009
163
I finally got to see the inside of a voltage transformer as one happened to blow up and I got to view a part of it. The wild thing was that since it was a 7200 volt transformer I thought that there would be some thick wire in there. Well, the top portion of it has one little itty bitty wire traveling through it and it blew my mind that it could carry such high voltage without difficulty, well, unless somehow a high current load is drawn through it causing it to blow. Heh
Here is the pic of what I'm talking about:
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Ok, so then what is voltage? I have read many times about how it's what pushes current. But what the heck is "THIS", the this that's pushing? I get the idea that current is the atoms moving through something. Current I can imagine. But voltage? I can't imagine what voltage is. How can something push when it's not anything at all?
What gives????

P.S. And why can so much voltage transfer through such a small wire? It's weird how the wire connecting to the top is so thick....

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#### MikeML

Joined Oct 2, 2009
5,444
The whole reason that the power company uses such high voltage to transmit power from one place to another is because stepping up the voltage steps down the current by the same factor. Because resistive losses in the wires are proportional to current squared, then high voltage-low current is much more efficient.

A #12AWG wire can carry 20A. If your line voltage is 120V, that means that circuit can deliver P=I*E = 20A * 120V = 2400W. Now imagine you want to deliver that same 2400W somewhere at 7200V. The current along that wire would only be I=P/E=2400/7200= 0.33A or 330mA. Think you could carry that in a smaller wire?

#### loosewire

Joined Apr 25, 2008
1,686
Is that wire part of the secondary.The wire is that a small piece.

#### loosewire

Joined Apr 25, 2008
1,686
Be nice, then explain please. thanks looosewire -----I should have read the op's name.

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#### foolios

Joined Feb 4, 2009
163
Is that wire part of the secondary.The wire is that a small piece.
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#### mik3

Joined Feb 4, 2008
4,843
The thickness of the wire is related to the current it conducts and not to the voltage across it. It is thin because the current is low. However, the insulation is very thick compared to the wire because the voltage is very high.

#### EPhantom

Joined Oct 12, 2009
5
I thought that wires heat up because of wattage. Like with a resistor, if you put any voltage across it, and current is flowing, then you have a power loss over the resistor. Then the resistor translates the power loss (due to friction) into heat energy.

Why doesn't this apply with this wire, wouldn't 2400 watts fry that wire in an instant?

#### mik3

Joined Feb 4, 2008
4,843
I thought that wires heat up because of wattage. Like with a resistor, if you put any voltage across it, and current is flowing, then you have a power loss over the resistor. Then the resistor translates the power loss (due to friction) into heat energy.

Why doesn't this apply with this wire, wouldn't 2400 watts fry that wire in an instant?
2400W is the power the transformer can deliver to the load.

Let's say you have 120V and 30Amps, thus 3600W

The power dissipated by the wire is

Pw=(I^2)*Rwire

Rwire is small thus the power dissipated by the wire when passing 30 Amps is much less than 3600W.