Would the answer be a?
Which two forces balanced in the Millikan oil drop experiment
a) electric and gravitational
b) electric and magnetic
c) magnetic and gravitational
d) none of the above
yes, looking for ratio of charge to mass, knowing mass, could calculate charge (slight oversimplification) see:
http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Ryan_McAllister/Slide3.htm
To determine which two forces balanced in the Millikan oil drop experiment, let's analyze each option:
a) Electric and gravitational: In the Millikan oil drop experiment, the principle is to measure the charge of an oil drop by observing its motion under the influence of electric and gravitational forces. The electric force arises due to the charged plates in the apparatus, and the gravitational force arises due to the mass of the oil drop. So, option a) is correct.
b) Electric and magnetic: While magnetic forces can be involved in other experiments, in the Millikan oil drop experiment, only electric and gravitational forces are considered. Thus, option b) is incorrect.
c) Magnetic and gravitational: As mentioned above, the Millikan oil drop experiment does not involve magnetic forces. Therefore, option c) is incorrect.
d) None of the above: Since option a) (electric and gravitational) is the correct answer, option d) is incorrect.
In conclusion, the forces that balance in the Millikan oil drop experiment are electric and gravitational forces, making option a) the correct choice.