What's the Drift Velocity in a Copper Wire Carrying 0.50A?

[hoyy1kolko]

Homework Statement

A copper wire of diameter 2.00mm carries a current of 0.50A.The number of conducting electrons per metre cube of copper is 8.00 x 10^28.
a)Calculate the drift velocity of the conducting electrons.
b)What is the number of conducting electrons in 10.0cm length of the wire

Homework Equations

I=nave
v=I/nae

The Attempt at a Solution

a) I=nave
v=I/nae
= 0.50/(8.00x10^25)(1x10^-3)(1.6x10^-19)
=3.9 x 10^-5 ms^-1
b)I=nave
n=I/ave
=0.50/(1x10^-3)(3.9x10^-5 )(1.6x10^19)
=8.0x 10^-3

The answer that i get is wrong.i don't know why.I need help and explanation.Is it need to derivate the formula then calculate?Thank you.

 

[kuruman]

What formula did you use to calculate a?

 

[hoyy1kolko]

i don't know how to calculate a.I need help.

 

[kuruman]

i don't know how to calculate a.I need help.

We help those who help themselves. What does a represent? Look at the same place where you got the equation for the drift velocity.