Available information are the length of the cable, the cross section diameter of the cable, the voltage and the amperes. For example, what is the voltage drop across 100 feet of 6mm diameter copper cable from a 12 volt AC source at one end and having a 300 watt light at the other end? The current in the cable is 25 amps.
2006-10-21 00:51:27 · 2 answers · asked by Shiang 1 in Science & Mathematics ➔ Engineering
Use these two formulas:
V = I*R
R = rho*L/A
where:
V, I, and R are voltage, current, and resistance
rho is the electrical resistivity of the material the cable is made of (copper in your example)
L is the cable length
A is the cross-sectional area of the cable, which you can figure out from the diameter
2006-10-21 02:24:51 · answer #1 · answered by genericman1998 5 · 0⤊ 0⤋
If you can't be bothered to calculate the resistance of a wire by yourself, here is a table where you can look it up:
http://www.powerstream.com/Wire_Size.htm
So in your example, a 6mm cable has 0.186Ohm per 1000 feet.
At 25 Amp, you lose V = I * R = 25 * (0.186/1000*100) = 0.45 Volt.
2006-10-21 12:05:35 · answer #2 · answered by Marianna 6 · 0⤊ 0⤋