11.6 Exercise 1

A Hall probe consists of a copper strip, $n = 8.5 \times 10^{28}$ electrons per cubic meter, which is 2.0 cm wide and 0.10 cm thick. What is the magnetic field when I = 50 A and the Hall potential is (a) $4.0 \mu \text{V}$ and (b) $6.0 \mu \text{V} ?$