Two small hollow metal spheres hung on insulating threads attract one another as shown.
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Robert Millikan received a Nobel Prize for determining the charge on the electron. To do this, 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 10,000 N/C downward, a certain drop with a mass of 3.27 ×10–16kg remains suspended. a. What is the magnitude of the charge on this drop? b. The electric field is downward, but the electric force on the drop is upward. Explain why. c. If the distance between the plates is 0.01 m, what is the potential difference between the plates? d. 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. 2. An electric field E exists in the region between the two electrically charged parallel plates shown above. A beam of electrons of mass m, charge q, and velocity v enters the region through a small hole at position A. The electrons exit the region between the plates through a small hole at position B. Express your answers to the following questions in terms of the quantities m, q, E, θ, and v. Ignore the effects of gravity. a. i. On the diagram of the parallel plates above, draw and label a vector to show the direction of the electric field E between the plates. ii. On the following diagram, show the direction of the force(s) acting on an electron after it enters the region between the plates. iii. On the diagram of the parallel plates above, show the trajectory of an electron that will exit through the small hole at position B. b. Determine the magnitude of the acceleration of an electron after it has entered the region between the parallel plates. c. Determine the total time that it takes the electrons to go from position A to position B. d. Determine the distance d between positions A and B. e. Now assume that the effects of gravity cannot be ignored in this problem. How would the distance where the electron exits the region between the plates change for an electron entering the region at A?