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Integrated Concepts The classic Millikan oil drop
Chapter 16, Problem 62PE(choose chapter or problem)
Integrated Concepts The classic Millikan oil drop experiment was the first to obtain an accurate measurement of the charge on an electron. In it, oil drops were suspended against the gravitational force by a vertical electric field. (See Figure 18.58.) Given the oil drop to be 1.00 µm in radius and have a density of 920 kg/m3 : (a) Find the weight of the drop. (b) If the drop has a single excess electron, find the electric field strength needed to balance its weight.
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QUESTION:
Integrated Concepts The classic Millikan oil drop experiment was the first to obtain an accurate measurement of the charge on an electron. In it, oil drops were suspended against the gravitational force by a vertical electric field. (See Figure 18.58.) Given the oil drop to be 1.00 µm in radius and have a density of 920 kg/m3 : (a) Find the weight of the drop. (b) If the drop has a single excess electron, find the electric field strength needed to balance its weight.
ANSWER:Solution: In the question the classic Millikan oil drop experiment was the first to obtain an accurate measurement of the charge on an electron. Given the oil drop to be 1.00 µm in radius and have a density of 920 kg/m 3 Step 1 Refer to figure 18.58 provided in the textbook, (a) Find the weight of the drop We need to find the drop of the weight So we need to calculate from Newton’s law, W = mg Here, W is weight of the drop, m is the mass of oil drop and g is acceleration due to gravity. And the mass is rewritten as, m =V Here, is the density of oil and V is the volume of oil drop. So now we need to substitute t he ab ove tw o equation is V for m in m g for W = V g