If this isn’t a magic trick, why does the LED light up when it is not connected to the mains electricity or to an energy storage system like a battery?
It is because of a chemical reaction. A normal battery, for example, produces a very similar chemical reaction. In a primary generator, a battery or our lemon, we need a negative pole (cathode) and a positive pole (anode).
Inside they contain a conductive solution or electrolyte, the more acidic the better, which is why lemons and their citric acid are perfect for this experiment. All the solution does is carry the electrical charge between the two poles.
The anode in the lemon is the zinc coin, which is where oxidation occurs.
The cathode in the lemon is the metal nail, which is where the hydrogen ions in the lemon juice are produced.
The process is simple: the zinc coin loses electrons which are gained by the hydrogen ions. As the electrons are exchanged, the zinc dissolves in the citric acid as positive ions. Hydrogen bubbles are created at the nail as it gains electrons that pass, in turn, into the wire. Once the zinc coating on the coins has completely dissolved, the battery is spent. The movement of the electrons generates the electric current.
In addition, the series circuit stops the flow of current from being interrupted.
When you set up this series circuit with four lemon batteries it generates and transmits enough energy to light the LED. Amazing, right?
If you don't have any lemons, or you're keeping them to make lemonade, don’t worry! Apples or potatoes also work for this experiment.
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