How do batteries work?
This next project is going to take a basic look at how batteries and electricity work. This will be the first part of three projects that explore energy and heat. In this experiment we will build a battery out of lemons and explore how charging batteries works as well. In the next few weeks we will build a solar oven and make edible circuits and lights! So let’s get started!

First we need to gather some basic materials. Remember to ask an adult for help, we will need to use a knife!





Materials:

4 lemons

5 alligator clips with leads (different colors work best to avoid confusion)

4 shiny pennies

4 zinc platted (galvanized) washers

1 3V 20 mA LED light, a piezoelectric buzzer
or a solar powered calculator (I find the calculator
best, but any of the three work fine)

1 potato

1 6V battery

1 meat thermometer (32º - 212º)

A small pairing knife (remember to get adult help
when using sharp objects!)

Some of these might be hard to find,
I reccomend trying an electronics store like Radio Shack®.


This experiment works best when everything is at the same temperature, and better still room temperature. Leave all of your materials over night in the same place, a small box will work great so it’s all ‘put away.’

While we wait for everything to equalize in temperature, let’s look at how this will work. Take a look at your battery, it has a + sign on one side and a – sign on the other side. Inside batteries you will find there are two poles. One is positive (+), the other is negative (-). Surrounding these two poles inside the battery is an electrolyte solution, simply put a liquid that allows ions to flow and cause current to flow up the wire. For the system to work, you need to then complete the circuit. It’s like a big loop where electrons travel from home everyday to work, they then go home tired after working all day.
Ok, now that’s basically how batteries work. We are going to use lemons and their juice as the electrolyte solution. The pennies will serve as our (+) pole, and the washers as our (-) pole. We have to link several lemons together so generate enough electricity for this work. If one lemon worked all by its self, we would be driving lemon powered cars!

Below are two videos to help illustrate the project.


To start, let’s make sure our lemons are really
juicy inside. You can do this be rolling them between a table or other hard surface and your hand. This will break up the insides so that the juice can move around inside. Do this for all of your lemons!Next let’s carefully (with an adult around to help), cut 2 small slits in each lemon about 1 inch apart. Put a penny in one slit and a washer in the other slit of each lemon. Keep a small amount of the washers and pennies sticking out so you can clip it with your alligator clips! Line up your lemons so that they read left to right washer penny washer penny...
On the first washer clip a black alligator clip with lead. This will always be the color of negative (-). Choose any other color(except for red) and clip it to the penny on your first lemon, then clip the other end to the washer in the second lemon. Repeat this from left to right until you have one penny left, clip your red lead to this. Now your battery is ready!
Starting with the red lead, clip the other end to the red end on your calculator, buzzer or the long wire on the LED light. Now clip the black wire to the red end on your calculator. Make sure the metal of the alligator clips are touching metal on the calculator, LED or buzzer! If you are using a buzzer, you should hear it sound, the calculator you can flip over and actually use to calculate, and the LED light should light up dimly(try cupping your hands around it to see the light better. If this does not work, check all of your connections. Make sure that metal touches metal and that the leads are in the correct order!

Now we are ready to move onto the next part of the experiment. How can we recharge a battery? Because electrons move from the anode to the cathode pole, the anode must eventually run out of electrons. But, we can replace those by reversing the process. Because we are using chemistry to generate electricity when a battery operates, reversing the process causes a chemical reaction that normally gives off heat too.
Let’s start by cutting (remember to ask for help) two small slits in our potato just like we did to the lemons, about an inch apart. Again, place a washer in one slit and a shiny penny in the other. Insert the meat thermometer into the potato between the washer and the penny. Wait for about 1 minute (or for the temperature to stop changing) and record the temperature. Hook a red alligator clip to your 6 V battery on the (+) pole, then hook it to the washer. Now hook the black clip to the (-) pole and then to the penny. Almost instantly the temperature inside your potato will begin to rise. It will take about 20-30 minutes, but you should see the temperature change by as much as 10º. Do you think you could cook a potato with a battery? How long would it take? How many batteries would you need?