: Any copper coin will work. (Canadian pennies from 1960 – 2001 all worked)

: Insert a penny into a cut on one side of the lemon. Push a galvanized nail into the other side of the lemon.

The nail and penny must not touch.

This is a single cell of a battery. The zinc nail and the copper penny are called electrodes.

All batteries have a “+” and “-” terminal. Electric current is a flow of atomic particles called electrons. Certain materials , called conductors, allow electrons to flow through them. Most metals (copper, iron) are good conductors of electricity. Electrons will flow from the “-” electrode of a battery, through a conductor, towards the “+” electrode of a battery.

Volts (voltage) is a measure of the force moving the electrons. (High voltage is dangerous!)

I have connected a volt meter to our single cell lemon battery. The meter tells us this lemon battery is creating a voltage of 0.906 volts.

Unfortunately this battery will not produce enough current (flowing electrons) to light a bulb.

To solve this problem we can combine battery cells to create higher voltages. Building more lemon batteries and connecting them with a metal wire from “+” to “-” adds the voltage from each cell.

The two lemon batteries above, combine to produce a voltage of 1.788 volts. This combination still does not create enough current to light a small bulb. Note the red wire connecting the batteries is joined from “+” (penny) to “-” (galvanized nail).

Four lemon batteries create a voltage of 3.50 volts. We should be able to light up a small device like an LED (Light Emitting Diode).

Note the connecting wires go from “+” to “-” on each battery.

LED

To turn on an LED you must determine the “+” and “-” connections. If you look closely at the red plastic base of an LED you will notice a “flat” spot (indicated by arrow above). The wire that comes out beside the flat spot must connect to the “-” side of a battery, the other wire to the “+” side.

In the above image, electrons flow from the “-” (nail) end of our lemon battery through the LED (making it glow) then back to the “+” (penny) end of the battery. This is an electronic circuit. The LED glows dimly with this configuration.

The quality of the copper and zinc can be a problem for a battery like this. Pennies in particular are rarely pure copper.

Try substituting a length of 14 gauge copper wire (common house wire) for the penny. Experiment with different lengths and configurations of electrodes. Other sources of zinc and copper may be found in the plumbing supply department of a hardware store.

The first battery was created in 1799 by Alessandro Volta . Today batteries provide the power for an amazing variety of devices, everything from flashlights to robots, computers, satellites and cars. Inventors and researchers continue to improve the battery, designing batteries that last longer and that are more friendly to our environment.

Understanding how batteries actually work requires a knowledge of chemistry. The most important factor in battery design is the electrical relationship between the two metals used in the battery. Some metals give electrons away while other metals accept extra electrons. Chemists have investigated metals and created an “electric potential” table comparing different metals.