What is the relationship between heat loss and resistivity in a cable?

[dinhjeffrey]

Homework Statement

http://img710.imageshack.us/i/2631001.jpg/
#29

Homework Equations

p=I^2R
P=IV

The Attempt at a Solution

well, the answer is D, but i don't see why the length matters? can anyone find out the equation for this problem?
i thought it was B) cable B because it has more resistivity

 

[Salamon]

The resistance of a conductor can be found using the equation,

R = p*l/A

where R = resistance, p = resistivity, l = length of conductor, and A =cross sectional area of conductor.

Length matters because the longer a resistor is, the more it can obstruct the flow of charge.