A slab made of unknown material is connected to a power supply as shown in Figure 21.107. There is a uniform magnetic field of 0.7 tesla pointing upward throughout this region (perpendicular to the...

A slab made of unknown material is connected to a power supply as shown in Figure 21.107. There is a uniform magnetic

field of 0.7 tesla pointing upward throughout this region (perpendicular to the horizontal slab). Two voltmeters are

connected to the slab and read steady voltages as shown. The connections across the slab are carefully placed directly across

from each other. Assume that there is only one kind of mobile charges in this material, but we don't know whether they are

positive or negative.