Question: A charged oil droplet is suspended motionless between two parallel plates (d = 0.01m) that are held at a potential difference V as shown in Fig. Periodically, the charge on the droplet changes, as in Millikan's original experiment. Each time the charge changes, V is adjusted so that the droplet remains motionless. Here is a table of recorded values of the voltage V :

i. 350.0 volts.

ii. 408.3 volts.

iii. 490.0 volts.

iv. 612.5 volts.

a. In which case is the charge on the droplet the greatest?

b. From the data above, determine the charge on the droplet for case (i) above. What assumptions do you need to make? (Hint: the ratio of voltages = ?)

c. Find the magnitude and direction of the electric field in case (i) above.

d. What is the mass of the drop?

Fig. - An oil drop suspended in an electric field.