Lemon Battery Experiment

One classic science experiment used to demonstrate the fundamentals of a chemical battery system is that of a lemon battery. Lemon batteries are not capable of running motors, but they have the capacity to produce a dim glow in an LED. Batteries comprise two different metals: copper and zinc, immersed in an acidic solution. The copper metal functions as the positive electrode and the zinc metal functions as the negative electrode. All batteries have a "+" and "-" terminal. The acidic solution in the battery is called the electrolyte. In case of the lemon battery, the acidic lemon juice is an electrolyte, and helps to break down the atomic structure of the zinc and copper metals. This results in the release of individual electrons. The flow of individual electrons is called electricity. These electrons will flow from the negative terminal to the positive terminal of the battery. The measure of force of the moving electrons is called voltage. This is the concept behind the lemon battery experiment. However, creating successful lemon batteries is not easy.

How to Make a Lemon Battery

Requirements

• Lemon (fresh and juicy)
• Nail (2"galvanized, zinc-coated steel nail)
• Clean copper coin
• Sensitive voltmeter (found in the electrical supply section of a hardware store)

Lemon Battery Light Bulb Experiment

Step 1
The first step is to cut a slit into one side of the juicy lemon, and insert the clean copper coin into it. On the other side, insert the galvanized zinc nail. Ensure that the nail and coin do not touch each other. The coin and nail form the positive and negative electrodes respectively, thereby forming the single cell of the battery. The two oppositely charged electrodes will now permit the flow of electrons through them. The free electrons from the lemon juice will travel from the negative electrode (nail) to the positive electrode (coin).

Step 2
The rate at which the electrons flow is called voltage. The faster the electrons flow, the higher the voltage. The voltmeter will measure the rate of electron flow. If one connects the voltmeter to the electrodes, a voltage of 0.906 volts will be detected. However, this is not enough to light a bulb.

Step 3
To achieve enough voltage to light the bulb, one has to make more lemon batteries and connect them via a metal wire. The metal wire should connect the positive electrodes to the negative ones, and this will add voltage from each cell. Take four lemon batteries and join them together from positive to negative. A total voltage of 3.50 volts will be created, which is enough to light up a small light emitting diode or LED light.

Step 4
At the plastic base of an LED, one will find two wires and a 'flat spot'. The wire just besides the flat spot needs to be connected to the negative side of the battery, while the other wire needs to be connected to the positive terminal. The electrons flow from the nail end to the coin end, thereby forming an electronic circuit which causes the LED to glow dimly.

The above steps on how to make a lemon battery can help one make a lemon battery at home without much effort. LEDs work at even very low voltages (below 2V) and low currents. These LEDs get damaged if connected to batteries over 2 volts. Thus, they require resistors to control batteries which are rated over 2V. However, since lemon batteries produce low current, it is safe to connect an LED to it. However, in this lemon battery experiment, the copper coin can pose a problem. The coin should be pure copper. One can substitute a 14 gauge copper wire for the coin. One can try out different permutations and combinations of electrodes in the lemon battery experiment.