# Physics homework resistivity

1. Nov 16, 2003

### thunderstorm

hi, i am doing my physics homework at the moment, and i have got stuck on the last part of a question. it is asking for the resistivity of the wire- the values i have are
length of wire 2.5m, cross sectional area 2.0mm squared, current of 3.0a flowing through driven by p.d. of 4.5V. the first part of the question had me work out the resistance of the wire which i got as 1.5ohms.
i understand the equation for resistivity is
r= pl/a where p is the resistivity, l is length, a is area of wire and r is resistance?
so do i rearrange this equation to work it out? sorry for sounding stupid, i get confused easily and i'm not very good at rearranging equations, any tips? thanks

2. Nov 16, 2003

### Ambitwistor

Re: resistivity?

Yes, you just rearrange the equation. Be careful to use consistent units: e.g., convert the cross-sectional area from square millimeters to square meters.