question involving resistivity using the formula?

einstein101

1. The problem statement, all variables and given/known data

The resistivity of nichrome wire is 1.1micro ohm meters. What length of wire of diameter 0.079 mm is required to provide resistance of 1.0 Kohm?

2. Relevant equations
R=resistivity x length/area


3. The attempt at a solution

1000ohms = ? x 0.0011/0.079

79 = ? x 0.0011

71818.18 = resistivity

I know I've stuffed up real bad, but this one is troubling me crazy.

ehild

What does "area " mean in the formula for resistance? What is the area for the 0.079 mm wire?

ehild

einstein101

Area relates to the 0.079 mm of wire. In the question it doesn't say mm squared. the answer is supposed to be 4.5 meters.

ehild

The diameter of the wire is 0.079 mm. The cross-section of a wire is a circle usually. The area in the formula means the area of the cross section of the wire.


ehild

Emilyjoint

I got 4.5m for the length.
I think you have mixed up the units.
resistiuvity = 1.1x10^-6ohm.metre
radius of wire = 0.0395x10^-3m

einstein101

Thanks Emily I got the answer too now. You were right I was mixing the units up.

Emilyjoint

Hey Einstein....thanks...great help someone else