Batteries store chemical energy that can be transmitted as electrical energy through various components in a circuit. You can think of the circuit as the path the electrons (electricity) take. The path has to have no breaks in it and it much be a path made of a material that will allow the electrons to flow (e.g. most metals although some are better conductors than others).
Batteries, such as the one we are about to build, have electrodes, or the connection points on the battery. The anode is the electrode at which electrons leave the cell and oxidation occurs, and the cathode is the electrode at which electrons enter the cell and reduction occurs. In our battery, the lemon juice acts as the electrolyte which is a solution which is electrically conductive. The electrolyte and electrode components cause a “flow” of electrons to occur as the two metals react with the citric acid in the lemons. When this reaction ends, the battery is dead.
- Cut three cardboard strips about 1 inch by 4 inch
- Wrap the three strips in aluminum foil
- Cut slits in each lemon about ½ inch apart
- Insert a alumni strip into one of the slits on each of the lemons
- Place a paperclip on the end of the aluminum strip
- In the other slit, place a 4 inch piece of copper tubing
- We will refer to your three lemons as Lemon A, Lemon B, and Lemon C. Using the copper wire, connect one end to the aluminum strip on Lemon A and the other end to the copper tubing on Lemon B. Take another wire and attach to the aluminum strip on Lemon B to the copper tube in Lemon C.
- Attach one end of a wire to the copper tubing on Lemon A. Leave the other end hanging.
- Attach another wire to the aluminum strip on Lemon C. Leave the other end hanging.
- Tape the free end of the wire from Lemon A to the positive terminal on the clock (or the millimeter).
- Tape the free end of the wire from Lemon C to the negative terminal of the clock.
- Wait a few minutes for the current to flow and the clock will begin to run.
If it doesn’t work well, make sure all the connections are good. You might also move the aluminum strips closer to the copper tubes (but not so close that they touch). Also make sure that the lemon has enough electrolyte (juice – dry lemons won’t work).
As explained above, an electrochemical reaction occurs between the aluminum tubing (the anode electrode), the copper tubing (the cathode electrode), and the lemon juice (the electrolyte). This reaction generates an electrical current. Real batteries that you buy in the store work in this exact same manner but use different materials for the electrolyte solution. Batteries were invented by a guy named Alessandro Volta.
You can take an old penny and an old dime (older coins were made with more pure metals) and stick them into the lemon about ¼ inch apart. Touch your tongue to the coins so that your tongue bridges the gap between them. You will feel the electricity tingling your tongue.