physics
posted by Rachel on .
A Halleffect probe operates with a 120 mA current. When the probe is placed in a uniform magnetic field of magnitude 0.0840 T, it produces a Hall voltage of 0.660 µV.
When it is used to measure an unknown magnetic field, the Hall voltage is 0.360 µV. What is the magnitude of the unknown field?
thank you helper

http://hyperphysics.phyastr.gsu.edu/hbase/magnetic/hall.html
It is directly proportional to B
B=.0840T*.360/.660 
oh ok sir thank you.
The thickness of the probe in the direction of B is 2.00 mm. Find the density of the charge carriers, each of which has charge of magnitude e).
thank you again sir 
see that link I gave you.

sir should i use this formula
V = IB/nqt
thanks you 
Yes, that will do it. I hope you understand where and how that was derived.
Here are links to it. If I wished to be head of the class, I would well understand this derivation:http://hyperphysics.phyastr.gsu.edu/hbase/magnetic/hall.html 
so sir in this formula.
I = 120mA
B = 0.0840 T
n = 8.47 * 10^28
q = 1.6 * 10 ^ 19
t = 2.00 mm
but how do i calculate d? 
d is the thickness of the plate. It should be given.