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…
The Mission Your mission, should you choose to accept it (ha ha, you have to!), is to complete the following tasks: • Find out what the Millikan Oil Drop Experiment is, and some background, such as when it was performed, … • Describe what was involved in the experiment. You must include a diagram of the apparatus and the physics principles behind the experiment. • You then do the experiment and make a conclusion.
Background • Create a file with the name: firstlastname.doc. Answer the following questions in that file, by finding QUALITY sites on the internet. BE SURE TO PROVIDE A LIST OF THE SITES YOU USED. • Q1: Where and when was Robert Millikan born? • Q2: Briefly describe how he became interested in elementary physics. • Q3: What was his earliest major success? • Q4: What was Millikan’s major contribution to the photoelectric effect equation? • Q5: When, and for what, did he win his Nobel Prize?
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 10 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 Autograph, plot a graph of charge (y – axis) versus ratio (x – axis). Make sure the unit of the charge is • 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? Show how you got this answer. (The ‘k’ means kilo)
Summary • Conclusion: Summarize your findings in paragraph form. • Email me your word document and your graph. The name of the document needs to be “firstlastname.doc” and the graph should be named “firstlastnamegraph.agg. Ex. hansolo.doc or lukeskywalkergraph.agg