Lemon Battery

How can I make a battery out of a lemon?

It's easy to make a voltaic cell with a lemon, a penny, and strip of zinc. Polish the zinc and the penny with a piece of sand paper. Squeeze the lemon without breaking through the peel to release the juices inside. Cut a pair of slits in the top of the lemon about 1-2 cm apart. Insert the penny in one slit and the zinc in the other. Touching the leads of a voltmeter to the penny and the zinc will show that a small voltage is produced.

If you don't have a voltmeter, a speaker from an old transistor radio can be used to detect the current. It will click when you touch the leads to the electrodes on the lemon cell.

If you've tried to hook a flashlight bulb up to the battery, you may have been disappointed. One lemon cell doesn't produce a lot of current. To light up a flashlight bulb, you'll probably have to connect several lemon cells in series. Connect the copper terminal of one lemon cell with the zinc terminal of another; attach the remaining copper and zinc electrodes to the bulb and try again. Chain more cells together if the bulb still won't light. (You've made a true battery, which is actually a lot of individual cells linked together.)

It is possible to light the bulb with just one lemon, if you add a few easily obtained electronic components (e. g. a capacitor) to your setup. See this article in the Journal of Chemical Education for details

Many other fruits and vegetables can be used for the cell. You can also use a silver or nickel coin in place of the penny, or a galvanized nail in place of the zinc strip. Soda pop or fruit juice in a cup can be used in place of the lemon. Can you use magnesium ribbon or freshly polished aluminum foil instead of zinc? Which combination of materials gives you the highest output voltage? Experiment!

If you build several different batteries you'll notice that the output voltage depends on the fruit, the electrode materials, the placement of the electrodes, and other factors. Combining an active metal with an inactive one works best; and juicy, acidic fruits work better than drier, more neutral ones.

Author: Fred Senese senese [at] antoine.frostburg.edu

source: http://antoine.frostburg.edu/chem/senese/101/redox/faq/lemon-battery.shtml