Question involving resistivity using the formula?

[einstein101]

Homework Statement

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?

Homework Equations

R=resistivity x length/area

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]

Homework Statement

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?

Homework Equations

R=resistivity x length/area

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