Chapter 28, Problem 36P

A Hall-effect probe operates with a 120-mA current. When the probe is placed in a uniform magnetic field of magnitude 0.080 0 T, it produces a Hall voltage of 0.700 μV. (a) When it is used to measure an unknown magnetic field, the Hall voltage is 0.330 μV. What is the magnitude of the unknown held? (b) The thickness of the probe in the direction of $\stackrel{\to }{B}$ is 2.00 mm. Find the density of the charge carriers, each of which has charge of magnitude e.