velocity approximation the motion of charge carriers in electric and magnetic fields does not lead to transverse magnetoresistance. The result is different with two car- rier types. OConsider a conductor with a concentration n of electrons of effective mass m, and relaxation time T; and a concentration p of holes of effective and relaxation time T. Treat the limit of very strong magnetic fields, w.T> 1. (n plec/B. (b) Show that the Hall field is given by, mass m. (a) Show in this limit that with Q = w.T, - 1 E, = - (n p) which vanishes if n = p. (c) Show that the effective conductivity in the x direction is -1 n + + (n - p O cf Ifn = p, o x B. If n + p, o saturates in strong fields; that is, it approaches a limit independent of B as B .