Maybe trick is not quite the right word, since there is no actual trickery here, just physics!
British one penny coins were originally (1971) made of bronze, an alloy consisting mainly of copper. But as metals like copper became more expensive, the coins were changed in 1992. Now they are copper plated steel, which makes the coins magnetic.
Bring a magnet up to the 1p coin, and it will be strongly attracted to the magnet. This attraction will also work through the thickness of a piece of wood.
However Tim’s home made apparatus also includes an arc of steel wire, and when the coin comes into contact with the wire, it sticks to the wire, even though this means it is slightly further from the magnet. As the magnet is moved to and fro, the coin moves along the wire. Most unexpected!
