17. The figure below represents the set-up of Millikan's oil drop experiment which was used by Millikan to determine the charge on an electron. Tiny droplets of oil in the form of mist are sprayed into the chamber P. Some of these droplets pass through the small hole in the metal plate I and are ionised by X-rays in chamber Q. If it is observed that an ionised oil droplet having a mass of \( 3.2 \times 10-14 kg \) and carrying a charge of \( -6.4 \times 10-19 C \), remains stationary between the metal plates I and II when a potential difference ' \( V \) ' is applied between the plates, then
(a) What is the direction of the applied electric field in chamber Q? Give a reason.
(b) What is the potential difference ' \( V \) ' applied between the metal plates, if the plates are separated by a distance of \( 1 cm \) ?
(Assume there is negligible drag force experienced by the oil droplet and take \( g =10 m / s 2 \) )