Magic Balloon

For a simple twist on a classic static electricity demonstration. Tie a string to a standard rubber balloon and charge it up with a piece of rabbit fur or wool sweater. Once it's charged you can stick it to the ceiling in the same way that it can be stuck to the wall.

​With this simple set up, observers will see the balloon on the ceiling and assume that it must be filled with helium. If the charge is strong enough (and the air dry enough), you can even use the string to pull it down a few centimeters and if the balloon will jump back up to the ceiling. Finally, once everyone is convinced that the balloon is filled with helium, pull the balloon down just enough so that the electrostatic charge is too weak to support the weight of the balloon and it sinks like the air-filled balloon that it is :)​

One of my favorite ways for students to explore this idea so that they can "see the charges" is to use the PhET Balloons and Static Electricity simulation.

In this sim, it is visible how the wall (or the ceiling) is becoming locally charge by induction as the negatively charged balloon gets closer to it. 

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