Today professor Eve and professor Owen create a lemon battery
For this experiment you will need:
Lemons, fresh and juicy lemons work the best! We used 6 lemons but you can make the experiment work with just 2.
Note – after the experiment do not eat the lemons as the experiment may turn them toxic!
Some copper and a galvanized nails. We brought these from our local hardware store, not all stores will stock copper nails but don’t worry any copper will do.
We used 6 of each but you can make it work with 2 of each.
Wires, any kind of wire will work. We used crocodile clip leads, but you con use regular wire and wrap it around the nails instead.
We used 10 although 3 will work fine.
An L.E.D. (light emitting diode). You will need an L.E.D. which needs between 1.5 – 2vdc.
You can find these online or at any electronics store. We got ours from eBay!
Lets get started! Step 1 – Make a battery
First roll the lemons in the palm of your hands or on a flat surface. This makes the lemons soft and juicy, the batteries will work much better this way 
Next carefully insert the copper and the galvanized nails into the lemon as shown below. Make sure the nails do not touch inside the lemon or it will not work as a battery!
Congratulations – You have just made a battery! If you want to make the simple 2 lemon series circuit repeat these 2 steps with another lemon. If you really want to make your L.E.D. glow brightly, try the 6 lemon parallel circuit – you will need a few more lemons 
Connect 2 lemon batteries in series with your L.E.D.
But first a quick note about L.E.D.s (light emitting diodes), a diode is an electronic component that only allows electrical current to flow through it one way. We must make sure we connect the L.E.D. the correct way or it will not work!
The negative terminal of the battery (galvanized nail) needs to connect to the negative leg of the L.E.D., we can tell which leg is negative in 2 ways, it is usually shorter than the positive leg and there is usually a flat on the L.E.D. on the same side as the negative leg.
Now we know how to connect the L.E.D., lets connect 2 lemon batteries to it in series as shown in the diagram below.
To connect the circuit in series, connect a wire from the positive leg of the L.E.D. (the long leg) to the positive electrode of the first lemon (the copper nail). Next connect the negative electrode of the first lemon (the galvanized nail) to the positive electrode of the second lemon. Finally connect the negative electrode of the second lemon to the negative leg of the L.E.D. (the short leg).
Each lemon produces around 0.8 volts, when connected in series as shown above the voltages of both lemons combine to give us around 1.6 volts – enough to make our L.E.D. glow!
However, the L.E.D. only glows dimly, this is because we haven’t got enough amps flowing in the circuit. In series the voltages of the lemons are added together but the amperage’s remain the same as in 1 lemon. To achieve a higher amperage we need to connect more lemons in parallel.
Connect 6 lemons in series and parallel with your L.E.D.
To give a brighter glow, add 4 more lemon batteries as shown in the diagram below:
We have added 2 extra pairs of lemons in parallel. Each of the 3 pairs of lemons produce around 1.6 volts, when connected in parallel as shown above the voltage at the L.E.D. remains at 1.6 volts. However, in parallel the amperage now increases 3 times which makes our L.E.D. glow much brighter! :)
So how does it work?
A lemon battery changes chemical energy into electrical energy. When we insert the two different metals into the lemon, its acidic juice starts to react with the zinc of the galvanized nail and releases electrons to flow through our circuit and causes the L.E.D. to glow. This in simple terms is how our lemon battery works, for a more detailed description (for more advanced mini scientists) We recommend this site
Thanks for visiting, why not check out some of our other experiments?
What kind of led?
Hi Katie, here is a link to an ebay page where we got ours – these should work fine
http://www.ebay.co.uk/itm/50-X-2-PINS-3MM-Round-Red-LED-Light-Emitting-Diode-Lamp-/120657348574?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c17bd07de#ht_2831wt_1271
There is a full technical description there
I teach a science class and showed the kids the chromotography video. All the kids loved it and are now asking if the mini scientists have a video to go with our other topics. Are you going to be making any on the science of water? We would love to see more!!
Hi Alyssa, we are really glad your class enjoyed it! Our lab (a.k.a. over dining room!) is in the middle of some building work at present. As soon as it is done we’ll get the lab coats back on and do a few water based projects