One can make a homemade capacitor using an aluminum foil and a plastic or a wooden stick (it's important that the stick is an insulator). Make a small ball out of the aluminum foil and wrap it around the stick. Then make a wider foil sphere around the ball so that they don't touch, and your capacitor is ready!
If the radius of the smaller ball is \(5~\mbox{cm}\) and of the bigger sphere \( 15~\mbox{cm}\), which capacitance in pF do you expect to obtain?
Details and assumptions
by
David Mattingly
