An n-doped silicon bar of cross-section 4.0 mm2 carries a current of 8.0 mA. The number density of mobile electrons in the bar is 1.0×1022 m−3.
(i) Calculate the drift velocity of the electrons.
(ii) The bar is now illuminated so that additional holes are generated, each having charge +e and the same number density as the electrons. The total current remains 8.0 mA. Assuming the drift velocities of electrons and holes are equal in magnitude, determine the new drift velocity of the electrons.
(iii) By what factor has the electron drift velocity changed as a result of illumination?