# Calculate the resistance of iron if

1. May 9, 2008

### looi76

1. The problem statement, all variables and given/known data
A rectangle bar of iron is $$2cm$$ by $$2cm$$ in cross section. Calculate its resistance if the resistivity of iron is $$11 \times 10^{-8}\Omega{m}$$.

2. Relevant equations

$$R = \frac{Pl}{A}$$

3. The attempt at a solution

$$R = \frac{Pl}{A}$$

$$A = 2 \times 2 \times 10^-4 = 4 \times 10^{-4}m$$
$$P = 11 \times 10^{-8}\Omega{m}$$

How is it possible to find the resistance If I don't have the length?

2. May 9, 2008

### G01

It isn't.

Maybe they are looking for the resistance per unit length:

$$\frac{R}{\ell}=\frac{\rho}{A}$$