Demo videos: electrostatics, electric current, and electrical power

Demonstration videos illustrating key concepts of electrostatics, electric current, and electrical power.

For other videos from our demonstration collection, please visit Physics Demo Videos. You may also wish to view our Video Lecture Series for short tutorials on topics from first year physics.

[Note: if you get an error message on playing the video, try clearing your browser’s cache and cookies, or try viewing in an incognito window.]

Electrical charges
Electroscope. As the charged rod is brought close to the knob, opposite charges are attracted by it into the knob. This leaves the post and silver leaf with the same charge. Thus, they repel each other and the leaf moves out. Why does the behavior reverse after the instructor touches the post?
Charged balloons. A charged balloon will stick to an uncharged wall.
Electrostatic Pom Pom. In the presence of a charged rod, a tissue pom pom will puff due to the repulsion of the ends.
Charged pith balls. Pith balls can be attracted to the rod or can be made to repel each other.
Wimshurst Machine. Static charge buildup can be seen as sparks between the two knobs.
Wimshurst Machine — charged bells. Static charge buildup on the bells attracts small metal balls, making them ring.
Wimshurst Machine; hail storm. Static charge buildup on the bottom plate and balls repels the balls, making them jump. They discharge on the top electrode and fall back down.
Van de Graaff. The Van de Graaff builds up a high static charge so that electric fields and charge transfer effects can easily be observed. Notice that the spark are initiated preferentially at a sharp point rather than a ball; this is how lightning rods work.
Electric force and Coulomb’s Law
Electrostatic Ruler. The force between the charged rod and the ruler can be used to turn the ruler.
Electrostatic Yard Stick. The force between the two charges can be used to turn the yard (or meter) stick.
Electric current, power, and Ohm’s Law
Conduction in Liquids. A bulb has two probes that make an open circuit when initially plugged into the socket. Placing the bulbs into ordinary tap water does not complete the circuit. However, add a dash of salt, and the ions are free to carry current, closing the circuit and making the light glow. The more salt, the brighter the bulb.
Fuse Wire. A piece of fuse wire is attached between two posts, completing the circuit. Light bulbs, in parallel, are added to the circuit by screwing them into their sockets. When the current load is too much for the wire, the fuse wire will burn and break, “blowing” the fuse and protecting the circuit. (Watch the fuse in the bottom right of the video, just to the right of the smallest bulb.)
Short a Capacitor. A large capacitor is charged through a resistor and then is shorted by touching the leads together. It gives a resounding CRACK and bright flash of light due to the quick loss of potential.
AC and DC Generator. A coil is spun in a magnetic field. Initially, the brushes contact rings attached to opposite ends of the coil, generating alternating current. When the brushes are moved to a split ring commutator, the generator puts out direct current.