Introduction: Franklin's Bells

About: Physicist
Franklin's bells were quite a novelty in the late 1700s.  Rather simple in its nature, the device consists of nothing more than a pair of bells, one connected to a stake in the ground and the other to a lightning rod. A light, conductive clapper would be put between them and during lightning storms, these bells would ring.

Since I was suffering from a lack of proper bells I chose to use aluminum cans for this experiment, and used a pull tab as a clapper. One can was kept at 0V while the other was charged to +35kV via a cockroft walton multiplier. Satisfactory and mildly annoying results were obtained.

Step 1: How They Work

How the device operates is actually rather simple. A metal clapper swings to one bell and gains a positive charge, where it's then repelled from the positive bell and attracted to the negative one. Upon impact the charge is lost and the clapper is once again attracted to the positive bell, and so the cycle repeats. Very little current is used in this process, so little in fact that the oxford electric bell, a battery powered Franklin bell, has been running continuously since it was set up in 1840.


The bells must be insulated from each other, and the charged one must be insulated from ground. The clapper must be insulated as well, hanging it from a cotton or polyester thread does a good job of that.

The potential difference between the two bells should be rather large for the device to work optimally; anything over 12kV should provide satisfactory results. Higher voltages cause the bells to ring more furiously, with a mild ring at 20kV and all hell breaking loose at 70kV.