We have an experiment on Hall Effect,in which we place a semiconductor material in the middle of a 2 poles of a magnet exactly in the middle so that a distance of 1 cm exists between the poles. Questions: 1.Why is a semiconductor placed?Will it make any difference with a metal? 2.Why a 1 cm gap in particular? 3.Why does it have to placed symmetrically w.r.t. to poles? 1.I think there should be no difference,but then since it is a practical experiments are there any constraints with using a metal? 2.I don't see why there has to be a 1 cm gap at all.There is a table on the apparatus that gives Magnetic field strength values for different magnet currents.But that won't be disturbed with the distance ,will it? 3.I am again not sure.Isn't the field the same everywhere in between the poles?