Harvey Fletcher and Robert A. Millikan conducted the oil drop experiment in 1909 to measure the charge of an electron. This experiment was conducted in the Ryerson Physical Laboratory at the University of Chicago. This experiment has also proven to be very important in physics.
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Definition: Oil Drop Experiment was an experiment that was designed to determine the charge of an electron. The value was found to be 1.60 ×10-19 C. |
Oil Drop Experiment Chemistry Questions with Solutions
Q-1: The purpose of Millikan’s oil drop experiment was to determine the charge on __________.
a) Electron
b) Proton
c) Neutron
d) Positron
Answer: a) Electron
Explanation: The purpose of Millikan’s oil drop experiment was to determine the charge on the electron.
Q-2: Which of the following factors determines the extent of deflection of the electron in Millikan’s experiment?
a) Charge on the electron
b) Mass of the electron
c) Electric and magnetic field strengths
d) All of the above
Answer: d) All of the above
Explanation: Millikan’s experiment is based on the principle that the amount of deflection of the electron depends on its charge, mass, and strength of the electric and magnetic fields.
Q-3: Why was ordinary oil not recommended in Millikan’s experiment?
Answer: Ordinary oil was not used in the experiment because it would evaporate due to the heat of the light, potentially resulting in an error in the Millikan’s Oil Drop Experiment. As a result, the oil commonly used in vacuum apparatuses with low vapour pressure was used.
Q-4: What kind of rays were used to irradiate the air between the plates?
a) Gamma rays
b) X-rays
c) Infrared rays
d) Microwave rays
Answer: b) X-rays
Q-5: Which device is used to measure the rate of fall of oil droplets due to gravitational force?
Answer: Telescopes are used to measure the rate at which oil droplets fall due to gravitational force.
Q-6: Which scientist, in addition to Millikan, devised the Oil drop experiment?
a) Thomson
b) Chadwick
c) Harvey Fletcher
d) Heisenberg
Answer: c) Harvey Fletcher
Explanation: The Millikan’s Oil Drop Experiment was carried out in 1909 by Robert A. Millikan and Harvey Fletcher to determine the charge of an electron.
Q-7: Give an outline of the Millkan’s Oil Drop Experiment apparatus.
Answer: Milliken and Fletcher built the apparatus for the experiment. It consisted of two metal plates held apart by an insulated rod. In the plate, there were four holes, three of which allowed light to pass through and one of which allowed viewing through the microscope. The experiment did not use regular oil. As a result, the oil commonly used in vacuum apparatuses with low vapour pressure was used.
Q-8: What was the significance of Millikan’s oil drop experiment?
Answer: Millikan’s experiment is crucial because it determines the charge of an electron. Millikan balanced the actions of electric, gravitational, and air drag forces using a simple apparatus. Using the apparatus, he calculated the charge on an electron to be 1.60 ×10-19 C.
Q-9: Match Column I with Column II.
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Column I |
Column II |
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A) William Crookes |
i) Watermelon model |
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B) J.J Thomson |
ii) Charge on the electron |
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C) Rutherford’s experiment |
iii) Black body radiation |
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D) Max Planck |
iv) Existence of nucleus |
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E) Millikan’s oil drop experiment |
v) Conduction of electricity through gases |
Answer: A)-v), B)-i), C)-iv), D)-iii), E)-ii)
Q-10: The charge on an oil drop in Millikan’s oil drop experiment is calculated to be 11.2 x 10-19C. Calculate the number of extra electrons on the drop.
Answer: As we know, Q = ne
Number of electrons, n = Q/e
Number of electrons, n = 11.2 x 10-19C/ 1.60 ×10-19 C.
Number of electrons, n = 7
Q-11: What was the charge on the electron measured in units of esu?
Answer: The charge on the electron was found by RA Millikan with the help of his oil drop experiment. The value was found to be 4.8 ×10-10 esu.
Q-12: Explain the Millikan’s Oil Drop Experiment procedure.
Answer:
- The atomiser emits a spray of oil droplets. These droplets are then allowed to enter an electrical condenser through a tiny hole in the upper plate (consisting of two charged plates).
- A telescope was used to observe the rate of fall of these droplets under the influence of gravity. The mass of the oil could be calculated from this.
- The air in the space between the plates was then irradiated by exposing it to X-rays. As a result, it ionises.
- The oil droplets capture one or more of the electrons that are thus knocked out. As a result, they become negatively charged. When a voltage is applied between the two plates, the oil droplet is attracted to the upper plate, which is positively charged.
- Again, by properly burying the voltage, a balance between gravitational and electrical forces can be obtained. As a result, the drop will come to a stop.
- The charge on the droplet was calculated using the mass of the oil droplet and the charge on the plates. It was discovered to be 1.60 ×10-19 C.
Q-13: How can you define an electron?
Answer: An electron is a fundamental particle with one unit negative charge and a mass nearly equal to (1/1837)th of a hydrogen atom.
Q-14: How did the gold foil experiment of Rutherford differ from Millikan’s oil drop experiment?
Answer: Rutherford’s gold foil experiment discovered the nucleus, while Millikan’s oil drop experiment determined the charge on the electron.
Q-15: What did Millikan’s oil drop experiment reveal?
Answer: Millikan oil-drop test was first carried out in 1909 by American physicist Robert A. Millikan. He discovered that all of the drops had charges that were multiples of a single integer, the fundamental charge of an electron.
Practice Questions on Oil Drop Experiment
Q-1: The oil used in Millikan’s oil drop experiment had to have _____.
a) High vapour pressure
b) Low vapour pressure
c) Intermediate vapour Pressure
d) High viscosity
Q-2: Which of the following was used to generate the oil droplet spray?
a) Telescope
b) Atomiser
c) Electrical condenser
d) Electrical forces
Q-3: What was the result of Millikan’s oil drop experiment?
Q-4: Calculate the electron mass using the values of e/m and e, which are 1.76 x108 C/g and 1.6 x 10-19 C, respectively.
Q-5: What is the use of X-rays in the Millikan’s Oil drop Experiment?
Click the PDF to check the answers for Practice Questions.
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