Science Buddies: "Ask an Expert"

Hi, I am doing your experiment "Where there is a charge, there can be sparks." I have done a couple of things differently, but I just wanted to make sure my idea of how this experiment works is correct. First I charge a balloon with a scarf. The balloon and scarf are neutral until I rub them together, and then friction causes the balloon's protons to strip electrons from the scarf. Thus the balloon becomes negatively charged and the scarf is left positively charged. Next I rub the nail head of the Leyden jar to the balloon, and the Leyden jar takes the electrons from the balloon and becomes negatively charged, leaving the balloon positively charged. When the negative charges enter the Leyden jar, it forces the positive charges to the outside of the jar. Than, when the Leyden jar is in the soap dish and the wire is attached (the wire transmits positive charges on the outside of the jar to the aluminum plate, where the protons will be stored), I push it toward the aluminum plate, and a spark is created by the attraction caused by the positive and negative charges coming together. And voila, you have created a tiny lightning bolt.
Is my understanding of this right? Also, would an electrophorus affect the charges? Thanks!
~Hannahpro

Hannahpro - I think you have most of the actions right. The balloon picks up a significant negative charge from the scarf, but when it contacts the nail of the Leyden jar, it transfers a significant charge to the jar. The balloon itself then does not become positively charged. It still possesses a negative charge, because in the transfer, it only reaches voltage equilibrium with the Leyden jar. It is still negatively charged (at a lesser magnitude) until it discharges further to another more positively charged object or to ground. In this experiment, the balloon is the electrophorus as it provides the negative charge to the Leyden jar and induces the positive charge to the other terminal of the jar.

Rick Marz