Rough science and homemade batteries

Rough science is the Open University's popular science programme on BBC2 in which five scientists are set scientific challenges, which they have to complete using natural resources. Inspired by this series, investigations involving simple batteries made from items found in the home or school laboratory can help KS3 pupils understand the origin of current, voltage and power, and the chemistry that drives batteries.

A simple battery can be made by pushing a screw (best if it is zinc-coated/galvanised) and a piece of copper into a lemon and connecting these two electrodes using wires to the device you want to power. This cell can produce enough power to run an LCD clock/watch. Using a carbon-rod electrode instead of the copper also works, and you can use potatoes as well as lemons. Three potatoes, each having a carbon rod and a galvanised screw electrode system can be wired up and will supply enough power to light a light emitting diode (LED). How a pair of electrodes produces a voltage when immersed in an electrolyte is revisited in the Box.