Making an Earth Battery

Moist earth is used as an electrolyte to create electricity in a voltaic cell. In 1841, Alexander Bain (1810 – 1877) demonstrated the ability of moist dirt to aid in generating electricity. Thus an “earth battery” is a pair of electrodes, of two dissimilar metals, with moist earth used as an electrolyte. To create the battery, Bain buried plates of zinc (anode) and copper (cathode) in the ground about one meter (3.2 feet) apart producing an output voltage of approximately 1 volt.

Have students create earth electrodes out of two dissimilar metals. Ask them to hypothesize what soil conditions are best for creating an earth battery. (Suggestions include: swamp or marsh muds, dry sand (no moisture), lawn soils, clay, sandy soils, acid forest soils, salty soils on roadsides after a season of winter salting.)

  • Go hunting for iron bacteria (see Blog: Hunting Iron Bacteria) and use these iron-rich muds as the battery source material.
  • How much power [W = I * V)] does your earth battery produce?
  • Could you create a series circuit (current passes through each circuit element in turn without branching) to power a small LED?
  • Download this PDF to learn how to create earth electrodes, make an earth battery, and calculate earth battery power: