Exam-style question
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What is the principle behind Millikan's oil-drop experiment?.
- A.It measures the mass of electrons directly.
- B.It determines the charge of an electron by balancing gravitational and electric forces.
- C.It uses cathode rays to measure electron speed.
- D.It calculates the energy levels of electrons in an atom.
Model answer
What a good answer should say
- It determines the charge of an electron by balancing gravitational and electric forces.
Explanation
Why this works
Millikan's oil-drop experiment involves balancing the gravitational force acting on charged oil droplets with an electric force, allowing for the determination of the charge of an electron.
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