MAGNETIC FIELDS IN MATTER — Edward Purcell & David Morin
Physics — E&M · rolled-capacitor-design
Problem
You have a supply of polyethylene tape, with dielectric constant 2.3, that is 2.25 inches wide and 0.001 inch thick; you also have a supply of aluminum tape that is 2 inches wide and 0.0005 inch thick. You want to make a capacitor of about 0.05 microfarad capacitance, in the form of a compact cylindrical roll. Describe how you might do this, estimating the amount of tape of each kind that would be needed, and the overall diameter of the finished capacitor. (It may help to look at Problem 3.21 and Exercise 3.57.)