Robert Millikan received a Nobel Prize for determining the charge on the electron. He set up a potential difference between two horizontal parallel metal plates. He then sprayed drops of oil between the plates and adjusted the potential difference until drops of a certain size remained suspended at rest between the plates, as shown above. Suppose that when the potential difference between the plates is adjusted until the electric field is 1.00 x 104 N/C downward, a certain drop with a mass of 3.27 10-16 kg remains suspended.

a. What is the charge on this drop? (4 marks)

b. If the distance between the plates is 0.010 m, what is the battery's potential? (3 marks)

c. The oil in the drop slowly evaporates while the drop is being observed, but the charge on the drop remains the same. Indicate whether the drop remains at rest, moves upward, or moves downward. Explain briefly, using equations to support your answer. (3 marks)

Oil Drop