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conantee
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« on: January 04, 2010, 04:21:01 AM »

50. The Hall effect is used in solid-state physics to measure
(A) ratio of charge to mass
(B) magnetic susceptibility
(C) the sign of the charge carriers
(D) the width of the gap between the conduction and valence bands
(E) Fermi energy
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conantee
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« Reply #1 on: January 13, 2010, 09:46:39 AM »

If you still remember what the Hall effect is, you should get the answer right away. The Hall effect is the phenomenon that there is a voltage difference across the conductor, whose direction is perpendicular to the pre-existing electric current and the magnetic field. This occurs just because the charge carriers have a Lorentz force acting on to it in the direction perpendicular to both magnetic field and velocity (i.e. current). The direction of force, also the voltage, depends also on the sign of charge carriers.

The correct answer is then (C). 51 of 100 people got the correct answer.
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