Try This at Home: Electrophorus
- Electricity is the flow of tiny, negatively-charged particles called electrons.
- A conductor is a material that allows electricity to flow through it.
- An insulator is a material that does not allow electricity to flow through it.
- Opposite charges attract each other, and like charges repel each other
What You Need
- 1 Styrofoam cup
- 2 Styrofoam plates (or 1 Styrofoam plate and 1 aluminum pie plate)
- Aluminum foil (not needed if using the pie plate)
- Wool fabric (like an old sweater or sock)
What To Do
- To make the top of the electrophorus, tape the Styrofoam cup in the middle of the top of a plate to act as an insulated handle. Completely cover the bottom of this plate in aluminum foil, wrapping some foil up around the edges to the top. Tape in place, if necessary. (Alternatively, use an aluminum pie plate, and just tape on the Styrofoam cup handle.)
- To make the bottom of the electrophorus, tape a Styrofoam plate to the table. Rub the plate hard with wool fabric for one minute.
- Using the cup handle, put the top of the electrophorus onto its bottom (so that the foil is sandwiched between the two plates). Touch the aluminum foil. What happens?
- Lift up the top of the electrophorus by the handle, at least 1 foot away from the other plate. Touch the aluminum foil again. What happens?
- Repeat steps 3 and 4 for as long as you would like to; if it stops working, recharge the Styrofoam plate by rubbing it with the wool again. See if you can spot a spark if you darken the room and bring your finger slowly toward the metal.
- Clean up.
An electrophorus is a device that carries an electric charge. By rubbing the wool against the Styrofoam plate, tiny, negatively-charged particles, called electrons, come off the wool and are left on the plate. Styrofoam is an insulator, a material that doesn’t let electrical charge pass through it, so the extra electrons are stuck on the plate, giving it a negative electric charge. However, aluminum foil is a conductor, a material that does allow electrons to move through it. The negative charge on the plate pushes the electrons in the foil away, and when you bring your hand near, some of the electrons jump to your hand, and you feel a shock!
After the negative charge is transferred from the foil to your body, the aluminum foil is left with a positive charge. When you touch it again, electrons from your body jump into the aluminum foil, and you feel another shock. This process can be repeated over and over, as long as the Styrofoam plate still has negative charge on it from being rubbed by the wool.
Every second, 50 to 100 lightning bolts strike the ground worldwide.