Magnetically Balancing Coins

By Paul Fears | 28 March 2017

Even Doctor Who would have been impressed by this balancing act. Four normal UK coins (5-pence, 1-pence, 10-pence and 2-pence) were balanced end-on-end on the rim of a Doctor Who TARDIS mug. Pretty impressive.

Coins magnetically balanced on the rim of a mug

This photograph is as taken. There has been no post-processing of the photo to add in the coins. These four coins are actually balancing on the rim of the mug. But how?

Just trying to get the largest 2-pence coin to balance on the rim was nearly impossible, but then adding three more coins simply compounded the problem. We found that we needed some assistance, just like The Doctor.

The Magnetic Science

There is a magnetic solution to the problem. As shown in the second photograph, positioned just above the mug are two magnet blocks suspended on a non-magnetic plastic support. These Magnets are projecting a magnetic field down towards the mug and the coins. By firstly building up the coins on the underside of the magnets (in order of size), the group of four can then be pulled down onto the edge of the mug. At this point, there is still just enough magnetic field to attract the top 5-pence piece without pulling it up onto the bottom of the magnet. Also, the magnetic field induced in the top 5-pence coin is transferred down through all the coins so that they all attract and hold each other in place.

And then, we have produced a vertical tower of coins magically perched on the edge of the mug.

The science behind magnets and magnetism has fascinated people for centuries. Magnetism is used by many magicians to perform illusions. The coin balancing trick is an example.