Practice Problems: 1. An oil dropr of mass 2.6 x 10"5 kg, is suspended between two parallel plates 0.50 cm apart. and remains stationary when the potential difference between the plates is 2?0 V. What is the charge on the oil drop. and how many excess or deficit electrons does it have? (4.7 x 10\"3 C. j: 3 electrons] 2. A metallic Ping-Pong ball, of mass 0.10 g, has a charge of 5.0 x 10-5 C. What potential difference, across a large parallel plate apparatus of separation 25 em, would be required to keep the hall stationary? {49 V] 3. An oil drop weighs 3.84 x 10-15 N. If it is suspended between tviio horizontal parallel plates where the electric field strength is 1.20 it 10" NEG. what is the magnitude of the charge on the oil drop? {3.2 110-"9 C, 2s) 4. An oil drop whose mass is 3.50 it 10'15 kg accelerates downward at a rate of 2.50 mils? when placed between two horizontal parallel plates that are 1.00 cm apart. Assuming that the oil drop is negatively charged and that the top plate is positive, how many excess electrons does the oil drop carry if the potential difference between the plates is 5.33 x 101' V? (4.?6 x 10'19 G] 5. An electron is accelerated upward at 5.2 We2 towards the positive plate when released. It the plates are set 15 mm apart. what is the potential difference applied across the plates? [-1.23 x 10'12 V] E. An oil drop with a mass of 7.20 x 10-15 kg is moving upward at a constant speed of 2.50 We between two horizontal parallel plates. If the electric field strength between these plates is 2.20 x 10" Wm, what is the magnitude of the charge on the oil drop? {3.2 x 10-19 C} 7. During a Millikan oil drop experiment, a student records the weight of five difference oil drops. A record is also made of the electric field intensity necessary to hold each drop stationary between the two horizontal parallel plates. at Using E as the manipulated variable. draw a graph showing the relationship between the weight and the electric field. b] Using only yew graph, determine the elementary charge. [about 1.6 x 10-19 C] Use this data for #7