Question

Hall-effect voltages are much greater for relatively poor conductors (such as germanium) than for good conductors (such as copper), for comparable currents, fields, and dimensions. Why?

Short answer

In metals the conductivity is larger, meaning that the difference inn the concentration of the electrons between two sides of the conductor plate will be small and we will need a large plate to observe the hall effect.

Step-by-step solution

Hall effect

Hall effect, discovered by Edwin Hall in 1879- is the production of voltage difference across the electrical conductor and to the applied magnetic field which is perpendicular to the current.

Hall effect for poor and good conductors

When a conductor carrying current is placed in a magnetic field, the charge carries experience force in many directions perpendicular to the flow of the current and the magnetic field. Result in developing of voltage in the edges of the conductor.

Now, we know that the voltage builds up as the resistance increase for example if we have two Resistors and both are connected in series with a battery. Then the resistor with the larger resistance will have a larger potential difference across it.

Or we can also say that the metals conductivity is larger meaning the difference in concentration of the electron between the two sides of the conductor plate will be small and we will need a large plate to observe the hall effect. The conductivity is inversely proportional to hall voltage.