# What is the current through the wire?

1. Sep 1, 2012

### november1992

1. The problem statement, all variables and given/known data
A 3 m long copper wire that has a diameter of 6 mm is connected to a 9 V battery.

a) What is the current through the wire?
b) If wire a was connected to a battery for 1 second, how much energy would the wire dissipate?

2. Relevant equations
A = $\pi$$r^{2}$
R = $\rho$$\frac{L}{A}$
i = $\frac{V}{R}$
$\rho$ = 1.72 x $10^{-8}$
P = i * V
W = P * t

3. The attempt at a solution

I got:
R = 1.82mΩ
i = 4945 A
p = 44505.45

I'm unsure of my answers. The values seem to be too high.

Last edited: Sep 1, 2012
2. Sep 2, 2012

### rude man

Your equations are all correct. Your R is too low by 2 orders of magnitude! Recompute A!

3. Sep 2, 2012

### november1992

Well, I tried to recalculate A and I got the same answer. I even used an online calculator and I got the same answer

A = $\pi$$r^{2}$
A = $\pi$ $(3 \times 10^{-3}) ^{2}$
A = $\pi$ (9 $\times$ $10^{-6}$)
A = 2.83 $\times$ $10^{-5}$

4. Sep 2, 2012

### rude man

3mm = 3 x 10-3 m?

That's news to me!

5. Sep 2, 2012

### november1992

I thought the prefix milli had a magnitude of $10^{-3}$?

6. Sep 2, 2012

### rude man

Er, oops, senior moment on my part. Of course that's right. And so is your original answer. Pardon my goof.