Video Transcript
Which of the following experiments
or theories related to the charge of an electron does the diagram represent? (A) Bohr’s model of the atom
theory. (B) Rutherford’s gold foil
experiment. (C) Millikan’s oil drop
experiment. (D) J.J. Thompson’s cathode ray
tube experiment. Or (E) Dalton’s atomic theory.
Experiments involving the device
shown sought to discover the charge of the electron. These experiments followed shortly
after the discovery of the electron by J.J. Thompson’s experiments. His work with cathode ray tubes
showed that electrons were negatively charged particles within the atom with a tiny
mass.
The experiment in the diagram built
off of this knowledge to discover the exact charge of this electron. Droplets of oil were passed through
a pinhole falling between two charged plates. At this point, they were ionized in
the air using radiation. And so the particles of oil became
charged. The scientists adjusted the voltage
across the two plates until the charged oil droplets stopped moving and attained a
state of mechanical equilibrium.
At this point of mechanical
equilibrium, the downward force of gravity, or in other words the droplets’ mass,
times the gravitational acceleration and the applied electric force or the charge
times the electric field were equal. From this, the scientists were able
to find the charge of the oil droplets. They found that all the oil
droplets had a charge that was a multiple of a base unit. They found that this fundamental
unit of charge was the charge of an electron. This experimental design is
attributed to Millikan and is now famously known as Millikan’s oil drop
experiment.
Therefore, the experiment or theory
related to the charge of an electron represented by the diagram is answer choice
(C), Millikan’s oil drop experiment.
