We typically describe charges as + and -. This convention was made in the 18th century by Benjamin Franklin. We can determine the sign of the charge on the tapes if we test them against something of known charge. By convention, if we vigorously rub an ebonite rod with a piece of fur, the ebonite rod will become negatively charged. Press one tape on the table and press a second on top of the first. Pull up both tapes together and then separate them. Charge the plastic pen by rubbing it vigorously with a piece of cloth, towel, etc. It should get negative charge through friction. Test the pen against each of the tapes. 11) Describe your results. 12) What is the sign of the charge on the bottom tape? Explain. 13) What is the sign of the charge on the top tape? Explain. 14) If you pull up a tape by itself it gets a negative charge. From where does the tape obtain the excess electrons? Explain. 15) After charging the tape, what is the sign of the object from which the tape received the excess electrons? Explain. 16) Summarize what you have learned about charged objects and the force between charges from this lab activity.