Lab 3: Coulomb's Law

The goal of this lab is to create a graph of the Coulomb Force as a function of distance between two charged tapes and determine if this obey's Coulomb's law which says that force is proportional to 1/r^2.

Force as a function of distance

• The goal is to create a graph of the magnitude of the Coulomb force as function of separation between the two tapes.
• hint: The U and L tapes will not maintain their excess charges forever - so take your measurements as soon as you make the two U (or L) tapes.
• hint #2: You must be VERY careful with your measurements. You will be measuring small differences in position, so be meticulous.
• Create two U (or L) tapes and hang them so that the handle is at the top. Hang them on the two stands so that you can move them easily. (Actually, it is easiest to just keep one stationary and move one).
• You will be taking two measurements (both with an associated uncertainty). r is the separation between the tapes meausred at the top. d is the deflection of one of the tapes (they should have the same deflection).
• The best way to measure the deflection is to use a reference point on the table.
• From d you can calculate the tangnet of the angle at which the tape is hanging. As with the previous part, the Coulomb force is proportional to the tangent of the angle. Thus ploting tangent of the angle is similar to plotting the Coulomb force.
• Plot tan(theta) versus r with Excel. Add a trendline of the type "power" and include the equation on graph. If these really acted like point charges - what should the "power" that Excel reports be?