Questions on Oil Drop Experiment
Multiple-Choice Questions: Oil Drop Experiment
1. Who conducted the famous oil drop experiment?
A) J.J. Thomson
B) Ernest Rutherford
C) Robert Millikan
D) James Chadwick
E) Niels Bohr
2. The oil drop experiment was designed to measure:
A) The mass of the atom
B) The charge of the electron
C) The speed of light
D) The strength of magnetic fields
E) The atomic number of hydrogen
3. What substance was used in the oil drop experiment?
A) Mercury
B) Alcohol
C) Oil
D) Water
E) Helium
4. What method did Millikan use to charge the oil droplets?
A) Heating them
B) Passing them through a magnetic field
C) Passing them through X-rays
D) Mixing them with electrons
E) Bombarding them with protons
5. What was the key finding of the oil drop experiment?
A) Discovery of the nucleus
B) Existence of neutrons
C) Mass of the proton
D) Quantization of electric charge
E) Stability of isotopes
6. The electric field in Millikan’s experiment was used to:
A) Heat the oil
B) Accelerate the oil drops
C) Ionize the oil
D) Balance the gravitational force on oil drops
E) Neutralize the oil charge
7. Millikan calculated the electron’s charge to be approximately:
A) 1.6 × 10⁻¹⁹ C
B) 9.1 × 10⁻³¹ kg
C) 3.0 × 10⁸ m/s
D) 6.02 × 10²³ mol⁻¹
E) 4.8 × 10⁻¹⁰ esu
8. Millikan’s experiment helped confirm that electric charge is:
A) Random
B) Infinite
C) Continuous
D) Quantized
E) Zero
9. What force opposes gravity in the oil drop experiment?
A) Friction
B) Centripetal force
C) Normal force
D) Buoyant force
E) Electric force
10. Millikan determined the mass of an oil drop by observing:
A) Its color
B) Its acceleration
C) Its fall velocity without an electric field
D) Its temperature
E) Its pressure
11. In the oil drop experiment, the electric field was created by:
A) Electromagnets
B) Rotating plates
C) Heated coils
D) Parallel metal plates
E) Magnetic rings
12. Millikan’s experiment verified which fundamental constant?
A) Planck's constant
B) Avogadro’s number
C) Speed of light
D) Charge of the electron
E) Atomic weight of hydrogen
13. The oil drop experiment was first conducted in what year?
A) 1879
B) 1897
C) 1909
D) 1919
E) 1932
14. What helped Millikan visually track the oil drops?
A) An X-ray monitor
B) A microscope
C) A stroboscope
D) A telescope
E) A radar
15. The oil used in the experiment needed to:
A) Conduct electricity
B) Be magnetic
C) Evaporate quickly
D) Be very light and form tiny droplets
E) Dissolve in water
16. Why did Millikan use oil instead of water?
A) Oil is cheaper
B) Oil is easier to vaporize
C) Oil does not evaporate quickly
D) Oil is magnetic
E) Oil glows under X-rays
17. What did Millikan find about the charges on oil drops?
A) They were always even numbers
B) They were always random
C) They were always multiples of a fundamental unit
D) They were always negative
E) They were always zero
18. What physical constant was indirectly determined using Millikan’s result and Thomson’s e/m ratio?
A) Planck’s constant
B) Neutron mass
C) Proton number
D) Electron mass
E) Atomic radius
19. Which of the following best describes the oil drop experiment?
A) Demonstrated electrons orbit in shells
B) Measured the charge of an individual electron
C) Showed atoms are mostly empty space
D) Calculated atomic weight of gold
E) Proved existence of protons
20. The significance of Millikan’s work was that it:
A) Disproved the plum pudding model
B) Introduced the concept of radioactivity
C) Measured the exact value of electron charge
D) Discovered the neutron
E) Calculated the atomic number
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Answers with Explanations
1. C – Robert Millikan conducted the oil drop experiment.
2. B – It was designed to determine the charge of the electron.
3. C – Millikan used oil droplets in his experiment.
4. C – He ionized the droplets by exposing them to X-rays.
5. D – He found that electric charge is quantized, i.e., it occurs in discrete units.
6. D – The electric field countered gravitational pull on the charged droplets.
7. A – He measured the charge as approximately 1.6 × 10⁻¹⁹ coulombs.
8. D – Electric charge was shown to be quantized (not continuous).
9. E – The electric force was used to balance the oil drops against gravity.
10. C – He calculated mass from terminal velocity (falling without an electric field).
11. D – The field was set up using parallel metal plates.
12. D – Millikan measured the fundamental charge of the electron.
13. C – The oil drop experiment was first done in 1909.
14. B – Millikan used a microscope to view the oil droplets.
15. D – The oil had to form tiny, slow-falling droplets.
16. C – Water evaporates quickly; oil does not.
17. C – He discovered the charges were multiples of a basic unit (elementary charge).
18. D – Combining his result with Thomson’s e/m, Millikan found the electron’s mass.
19. B – The experiment measured the charge of individual electrons.
20. C – Millikan’s experiment determined the exact value of the electron’s charge.
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