The Millikan Oil Drop
Experiment
Measuring the elementary charge of
an electron
Introduction
No one has ever seen an electron. In fact, no
one has even seen an atom! So how do we
know the charge on the electron?
You are about to find out…
mg qE
Millikan’s Oil Drop Experiment
Your task in the experiment is to determine
the charge on various charged spheres by
balancing the weight of the spheres and the
electric force on them:
To perform this experiment, you must record
the mass of the spheres and the electric field
required to stop each drop.
Balance five drops – ensure that each drop
remains stationary for at least 6 seconds. In
addition, do not use electric field values
above 68kV/m.
Millikan’s Oil Drop ….
Make sure you record this information in a data
table.
Describe what was involved in the experiment.
You must include a diagram of the apparatus and
the physics principles behind the experiment.
Explain all of the pertinent mathematical
relationships
To perform this experiment, click here. You may
wish to click the Replace with new drops box.
Analysis
Using the lowest charge obtained, calculate the ratio of
every charge to that lowest charge: your first value is
1.00.
Using Excel, plot a graph of charge (y – axis) versus
ratio (x – axis). Make sure the unit of the charge is 1019 C
Choose a linear fit.
Save it to be emailed in.
Q5: What does the slope of the graph represent?
Q6: Compare this to the accepted value; calculate the
percent difference.
Q7: What is another, more common unit for kV/m?
Summary
Conclusion: Summarize your findings in
paragraph form.
Email me your word document and your graph
as part of that document. The name of the
document needs to be “firstlastname.doc”.
Ex. hansolo.doc