A simple Franklin Bells set up using high voltage from an (old style) CRT TV screen.
“Continue reading” for more details and photos.
There is a sheet of aluminium foil stuck to the screen. One can is free to swing back and forth and the other is fixed. The fixed can is earthed to a metal object that is mains earthed. Like the outside of a toaster. The best effect is when the screen is turned off and on when you can see sparks. These are simple static type sparks and are safe for you but not necessarily other electronic equipment. The right photo shows the can swinging in the longer exposure.
This is popularly attributed to Benjamin Franklin as an audible lightning detector but was described earlier by Andrew Gordon. These have a small swinging metal object between an earthed bell and a bell attached to the high voltage. The metal object picks up charge from the high voltage side and being similarly charged is repelled to the other side. As it touches (thereby ringing the bell), it transfers its charge to earth and swings back to repeat the process. A simple set-up is from SciToys.
Now if you have many swinging objects they will transfer charge to each other and end up with a chaotic motion and noise. Like a row of 10 cans…
The power off is off and all is quiet.
Once it is turned on to perhaps 50 kV the cans undergo a lot of agitated movement as shown in the longer exposure.
The sparks between cans are shown in the dark.
Now for some larger spheres to make a Franklin Bells setup. The large (12 inch) sphere is capable of being charged to a much higher voltage before breaking out and losing it. It is hung from a basketball hoop with fishing line.
The power is off here. The right ball (10 inch) is connected to my HV supply which will give 4 inch sparks from sharp points so perhaps 80kV. The earth is at the left and is a large metal sheet.
The 12 inch ball is a blur of motion as it swings through a 10 inch arc striking each side in turn with 1/2 inch (1.7cm) spark appearing as it comes close. This equates to at least 50KV according to spark gap tables. The right photo shows the spark at either end and a ruler for scale.
This setup above shows the size of the sparks from the supply which are about 4 inches. This is from a breakout point on the negative side. To and from a sphere the sparks are much smaller.
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Photo Date: 2008