Earth Science - Other

# How to Build a Simple Lemon Battery

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Did you know that you can create a battery using just three common things that you can find at home; a lemon, an object made from zinc and an object made from copper? This experiment is very popular in text books and is ideal for students to learn how a battery works with a simple hands on experiment.

What you will need :

-          a large juicy lemon (preferably fresh)

-          an object made from zinc : a galvanised nail coated in zinc, a dime or a zinc strip

-          an object made from copper : a copper coin ( a penny or any other copper coin) or a copper strip

-          a knife

-          voltmeter

-          connecting wires

Instructions :

1. Roll the lemon around on a table to ‘activate’ the juices in the lemon.

2. Using a knife, make a slit on the top left side of the lemon. Insert the copper object you wish to use.

3. Make another slit on the right side of the lemon. Insert the zinc object you wish to use. Make sure that the two objects do not touch.

4. Take two connecting wires and attach the objects to the voltmeter, making sure that you are connecting it in the right way. This will show you how many volts the lemon is producing.

Scientific Explanation :

A battery is made up of various cells, each containing an electrolyte, and two electrodes. In this experiment, the acidic juice of the lemon acts as the electrolyte, a liquid which allows electricity to pass through it. The two electrodes are the zinc and copper objects, materials called conductors. The electrodes are where the electric current enters or leaves the battery.

When the two electrodes come into contact with the acidic electrolyte, two half reactions start to occur, changing chemical energy into electrical energy. Electrons are supplied to the zinc through the cathode ( the negative electrode).

Half Reactions :

With the zinc: Zn → Zn2+ + 2 e-
At the copper: 2H++ 2e- → H2

When you close the lemon circuit, you are producing a voltage, although very low in this experiment; less than 1 Volt. This low voltage isn’t enough to light up even a small bulb. To increase the voltage, you could create more cells to form a battery. Build more lemon cells and combine them together using connecting wires, making sure that you connect the zinc object to the copper object. Also, make sure that you connect the cells in series so that the voltage is added together. You would need around four lemon cells to light a small LED (light emitting diode). Four lemon cells would give you around 3.5 Volts.

You could improve your battery by using more pure metals. Try to obtain pure pieces of zinc and copper so that you can gain more voltage.

Warnings!

This experiment is ideal for children in Grades 3 to 8.

Do not try this experiment with children under 5 years since they could choke on some of the small parts required when building the lemon battery.

When you have finished with the experiment, make sure that you dispose of the lemon and the metal objects safely.

Follow all of the directions given above precisely to enjoy a safe and fun experiment.

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