# AC Circuit Question

Discussion in 'General Electronics Chat' started by n7dgn, Jun 5, 2009.

1. ### n7dgn Thread Starter New Member

Jun 5, 2009
1
0
I have a question about AC circuits. I've read the whole section of AC circuits in the ebook, but there is still one thing I don't quite understand.

If you have an AC circuit with, say, an infinitely long conductor, how does the current travel down the wire? If the current is moving back and forth, it goes half a cycle (180deg) down the conductor half a wavelength, and then reverses direction and travels back the other half of the cycle half a wavelength, when/how does the current travel the next wavelength down the conductor, and then next, etc.

Doug

2. ### KL7AJ AAC Fanatic!

Nov 4, 2008
2,043
292
Greetings!

Congratulations on reading the entire A.C. section. I haven't even done that yet!

I believe you'll find your answer in the section on transmission lines. The infinite transmission line is used as a starting point for transmission line theory. Imagine a transmission line with an infinite number of series inductors and parallel capacitors. What happens is that it looks like a resistor of a value equal to the characteristic impedance. Since the current never actually reaches the far end all you see is an instantaneous "surge impedance"...actually an early term for characteristic impedance.

If you haven't read that section, please do. We're also doing an upgrade on the transmission line section. Hope this helps some!

Eric

3. ### mik3 Senior Member

Feb 4, 2008
4,846
63
In an AC circuit, electrons just oscillate around a position in the wire. They don't move around the wire like in a DC circuit.