<P> A lemon battery is a simple battery often made for the purpose of education . Typically, a piece of zinc metal (such as a galvanized nail) and a piece of copper (such as a penny) are inserted into a lemon and connected by wires . Power generated by reaction of the metals is used to power a small device such as a light emitting diode (LED). </P> <P> The lemon battery is similar to the first electrical battery invented in 1800 by Alessandro Volta, who used brine (salt water) instead of lemon juice . The lemon battery illustrates the type of chemical reaction (oxidation - reduction) that occurs in batteries . The zinc and copper are called the electrodes, and the juice inside the lemon is called the electrolyte . There are many variations of the lemon cell that use different fruits (or liquids) as electrolytes and metals other than zinc and copper as electrodes . </P> <P> There are numerous sets of instructions for making lemon batteries and for obtaining components such as light - emitting diodes (LEDs), electrical meters (multimeters), and zinc - coated (galvanized) nails and screws . Commercial "potato clock" science kits include electrodes and a low - voltage digital clock . After one cell is assembled, a multimeter can be used to measure the voltage or the electric current from the voltaic cell; a typical voltage is 0.9 V with lemons . Currents are more variable, but range up to about 1 mA (the larger the electrode surfaces, the bigger the current). For a more visible effect, lemon cells can be connected in series to power an LED (see illustration) or other devices . The series connection increases the voltage available to devices . Swartling and Morgan have published a list of low - voltage devices along with the corresponding number of lemon cells that were needed to power them; they included LEDs, piezeoelectric buzzers, and small digital clocks . With the zinc / copper electrodes, at least two lemon cells were needed for any of these devices . Substituting a magnesium electrode for the zinc electrode makes a cell with a larger voltage (1.5 − 1.6 V), and a single magnesium / copper cell will power some devices . Note that incandescent light bulbs from flashlights are not used because the lemon battery is not designed to produce enough electric current to light them . By multiplying the average current of a lemon (0.001 A / 1mA) by the average (lowest) voltage (potential difference) of a lemon (0.7 V) we can conclude that it would take more than 6 million lemons to give us the power of an average 4320W car battery . </P> <P> Many fruits and liquids can be used for the acidic electrolyte . Fruit is convenient, because it provides both the electrolyte and a simple way to support the electrodes . The acid involved in citrus fruits (lemons, oranges, grapefruits, etc .) is citric acid . The acidity, which is measured by the pH, varies substantially . </P>

How much electricity does a lemon battery produce