# What is the charge carrier density in the conductor

1. Apr 7, 2010

### uofcphysics

The Hall voltage across a 0.800-mm-thick conductor in a 1.30 T magnetic field is 3.2 uV when the current is 12.0 A.

What is the charge carrier denisty in the conductor (in m-3).

I was using the equation Vh=IB/ned
where Vh is the Hall voltage
I is the current
B is the magnetic field
n is the charge-carrier density
e is the charge of an electron
and d is the thickness

I rearranged to get n=IB/Vhed
and evaluated to get 3.806*1025m-3

But this came up wrong on the assignment and it looks like an unreasonable answer. I think I need additional values but basically this entire question is really confusing me.

Thanks for the help!

Last edited by a moderator: Apr 7, 2010
2. Apr 7, 2010

### nickjer

Please show us what numbers you used, and try to keep everything in SI units. Because I get a different answer than you when plugging in the numbers you gave.

3. Apr 7, 2010

### uofcphysics

I used the numbers I provided so:
I=12.0 A
B= 1.3 T
e= 1.6*10^(-19) C
V= 3.2*10^(-6) V
d= 0.8 mm (I left it because those are the units that the answer is in- but I'm guessing now that that is probably wrong).

What did I miss that is wrong in the calculation?

4. Apr 7, 2010

### nickjer

The units the answer is in is meters, not millimeters. So d = 8*10^-4 m.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook