- #1
subopolois
- 86
- 0
Homework Statement
i need to find the radius of a copper wire given the following data:
resistivity is 0.25 ohm meter
length of wire is 200 m
Homework Equations
roe=RS/I
roe=resistivity
R= resistance of material
S=cross sectional area
I= length of specimen
The Attempt at a Solution
i was looking at the equation and noticed i don't have any value for the resistance of the copper, so i looked it up online and it said: 0.00000001678 ohm.m. since i have 200m of wire i multiplied it by 200. so into the equation with everything:
0.25=3.356x10^-6 x s/200 meters
rearranging for the cross section area:
s= 21222410.9
although it doesn't say in the question, i assume that the cross section area of copper wire is circular. so i use the area of a circle to find the radius:
A= pi r^2
r= 2599 m
i don't know about you but this doesn't seem right, to have a wire with radius of 2.5 kilometers. I am stuck at what to do, my only guess is that the resistance value is wrong and i know there is and equation for resistance:
resistance= resistivity x length/area
i have the resisivity and the length, but what would i use for area?
help!