Lab Assignment: Millikan Oil Drop Experiment

The goal in this lab is simply to determine the value of the electric charge q_e employing Millikan's method. You'll have the Pasco AP-821A apparatus to help you though so it shouldn't take yoy as long.The procedure for doing this is well described by the Pasco manual linked below. Be sure you read that thoroughly before you begin to take data.

Some useful information and hints

• Read through the entire experimental procedures outlined in the manual and pay particular attention to how to analyze the data. It is a particularly nuanced process by which you can extract the value of e without knowing the number of charges deposited on oil drops. Also you may avail yourself of the excellent write up in Mellisinos and Napolitano and of course google can help you find many student papers online. If you do find useful sources on the web make sure cite them in your bibliography.
• This lab requires a lot of patience and careful observations of very small objects that appear through the microscope. The charged droplets are tiny and thus are influenced significantly by the ambient environment in ways you'll have to figure out how to control. Its good practice to have plan when you start your data taking. The manual provides you with useful hints but you will have to think up things to help on your own.
• As with all labs in this course a proper account of your experimental uncertainties is a must. As you determine parameters in your formulas and measure the variables make sure you take into proper account the experimental uncertainties and that these uncertainties are correctly propagated to determine your best estimate of the uncertatinty in your measurement. In this case that will be the value of the electrical charge. Keep in mind thought that the formula that relates the value of the charge to the various quantities you'll measure is somewhat complicated so propagation of errors can get somewhat involved. However, determing the relative uncertainty of each of the variables in the expression and ignoring those that are small relative to the others will help simplify things considerably. The way to do this is to consider the sources of uncertainties carefully by determinig the relative errors (err_val/val) of each measurement that goes into the formula. Please make sure that indicated what assumptions you make in determining the overall uncertainties in your write up. Documenting exactly what you did is of paramount importance so make sure you clearly describe this in your paper.
• The Pasco AP-8210A manual is: Millikan-Oil-Drop-Manual-AP-8210A-corrected.pdf

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