# Electric current

#### Dx

Hiya!
I have a problem thats got me confused to solve. I wanna use ohms law but not right. Here is the problem.

A nichrome wire has a radius 0f .5 mm and resistivity of 100 x 10^-8 ohm.m. If the wire carries a current of .5 A what is the voltage across the wire? The length of the wire is .32m

E = .5A x 100 x 10^-8 ohm is what i have for setting it up but its not the answer. what do i need to do to solve for this?

Dx

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#### Tom Mattson

Staff Emeritus
Gold Member
Originally posted by Dx
A nichrome wire has a radius 0f .5 mm and resistivity of 100 x 10^-8 ohm.m.
Note: You were given the radius and the resistivity. You were not given the resistance.

E = .5A x 100 x 10^-8 ohm is what i have for setting it up but its not the answer.
The problem is that you plugged the resistivity in for the resistance.

what do i need to do to solve for this?
Calculate the resistance, then use E=IR.

#### Dx

Re: Re: electric current

The problem is that you plugged the resistivity in for the resistance.

Calculate the resistance, then use E=IR. [/B][/QUOTE]

Ok i have the .5A but no E or R to perform ohms law with how do i solve for this please Tom.

Dx,

#### Tom Mattson

Staff Emeritus
Gold Member
Re: Re: Re: electric current

Originally posted by Dx
Ok i have the .5A but no E or R to perform ohms law with how do i solve for this please Tom.
1. They ask you for E.
2. They give you enough information to find R.

Look up the deinfition of resistivity, and you will see how it is related to the dimensions of the wire. Come on, this is easy. You can do it.

#### Dx

So Happy!

Thank You, Tom!

You know i looked at that section numerous times but after taking a days break and reading what you wrote it was like a lightbulb lit up in my head. I cant believe I didnt see it earlier always the simple ones that seem to give me the most trouble.

I found the formula R = p(L/A) then converted it to amps using ohms law.

Much appreciated, you helped me alot!
Dx