The device is operated by first frictionally charging a flat insulating plate called a "cake". In Volta's day, the cake was made of shellac/resin mixtures or a carnauba wax film deposited on glass. Nowadays, excellent substitutes are available. Teflon^TM, though a bit expensive, is a good choice because it is an excellent insulator, charges readily, and is easy to clean and maintain. The electrophorus is ideal for generating energetic capacitive sparks required for vapor ignition demonstrations.

The basic operational steps for the electrophorus are depicted in the sequence of diagrams below. Note that the electrode, though making intimate contact with the charged plate, actually charges by induction. No charge is removed from the

charged cake and, in principle, the electrode can be charged any number of times by repeating the steps depicted. Click here to view an animation of the electrophorus charging process.

The energy for each capacitive spark drawn from the electrophorus is actually supplied by the action of lifting the electrode off the cake. This statement can be confirmed by investigating the strength of the sparks as a function of the height to which the electrode is lifted. This can be empirically demonstrated by using an electroscope or a small fluorescent tube.

Today, the electrophorus is built in hundreds of secondary school demonstrations each year. If you would like to learn how to build one of your own from simple household apparatus, please see the separate article: {ElectrophorusExp.doc.}

Our electrophorus is constructed from an Aluminum pie pan, a Styrofoam plate and cup, some tape and a small Neon bulb.

Construct an electrophorus by taping the Styrofoam cup to the center of a pie pan. Separate the leads of the Neon bulb and tape one end to the edge of the pie pan.

The Neon bulb will clearly glow at 65V-90V, readily indicating typical static

electric charges.

Charge the Styrofoam plate be rubbing in against your hair and them place it on the table. Holding the pie pan with its handle (styro cup), place it on top of the plate. Be carefull not to touch the Aluminum with your hand. Touch the outer wire of the Neon bulb with your finger. You should draw a spark and light the bulb.

Now pick up the Al plate by the insulating handle, and again touch your finger to the outer wire of the Neon bulb. The light should again glow.