# Homework Help: Diameter and resistance

1. Feb 14, 2009

### phy112

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

If 46 m of nichrome wire is to have a resistance of 12.0 Ω at 20°C, what diameter wire should be used?

2. Relevant equations

R=$$\rho$$(L/A)

3. The attempt at a solution

I tried and I got 2.1. The $$\rho$$ of nichrome is 108e-8

2. Feb 14, 2009

### Mr.Amin

First solve for the variable you are looking for and put it on one side. Keep your knowns on the other side. Remember that A stands for area, and area is related to wire diameter.

I am online for a bit, so give it a go. DON'T FORGET YOU UNITS!

3. Feb 14, 2009

### phy112

ok yeah i got 2.3 mm. after i figured out A. I figured out diameter doing A=1/4pi(dsquared)

4. Feb 14, 2009

### phy112

ok i got it right. thanks!

5. Feb 14, 2009

### Mr.Amin

Good for you!