Lemon battery
Light up a diode... with a lemon!
Safety
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Put on protective gloves and eyewear.
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Conduct the experiment on the tray.
- Do not allow chemicals to come into contact with the eyes or mouth.
- Keep young children, animals and those not wearing eye protection away from the experimental area.
- Store this experimental set out of reach of children under 12 years of age.
- Clean all equipment after use.
- Make sure that all containers are fully closed and properly stored after use.
- Ensure that all empty containers are disposed of properly.
- Do not use any equipment which has not been supplied with the set or recommended in the instructions for use.
- Do not replace foodstuffs in original container. Dispose of immediately.
- In case of eye contact: Wash out eye with plenty of water, holding eye open if necessary. Seek immediate medical advice.
- If swallowed: Wash out mouth with water, drink some fresh water. Do not induce vomiting. Seek immediate medical advice.
- In case of inhalation: Remove person to fresh air.
- In case of skin contact and burns: Wash affected area with plenty of water for at least 10 minutes.
- In case of doubt, seek medical advice without delay. Take the chemical and its container with you.
- In case of injury always seek medical advice.
- The incorrect use of chemicals can cause injury and damage to health. Only carry out those experiments which are listed in the instructions.
- This experimental set is for use only by children over 12 years.
- Because children’s abilities vary so much, even within age groups, supervising adults should exercise discretion as to which experiments are suitable and safe for them. The instructions should enable supervisors to assess any experiment to establish its suitability for a particular child.
- The supervising adult should discuss the warnings and safety information with the child or children before commencing the experiments. Particular attention should be paid to the safe handling of acids, alkalis and flammable liquids.
- The area surrounding the experiment should be kept clear of any obstructions and away from the storage of food. It should be well lit and ventilated and close to a water supply. A solid table with a heat resistant top should be provided
- Substances in non-reclosable packaging should be used up (completely) during the course of one experiment, i.e. after opening the package.
FAQ and troubleshooting
The diode doesn’t light up. What to do?
First, ensure that the plates in a lemon do not touch each other.
Second, check the connection between the crocodile clips and the metal plates.
Third, make sure that the diode is connected correctly: the black crocodile clip should be connected to a short “leg”, and the red clip to a long one.
Importantly, crocodile clips shouldn’t touch the other “leg” to avoid short-circuiting!
Juice is hissing around the magnesium plate. Is it normal?
Everything is alright. Magnesium is an active metal, and it reacts with citric acid. The reactions yields magnesium citrate and releases hydrogen.
Step-by-step instructions
- Take 2 magnesium plates from the vial marked “Mg.”
- Take 2 crocodile clips: 1 black and 1 white. Clip the crocodile clips—black and white—onto the magnesium plates.
- Take 2 copper plates from the vial marked “Cu.”
- Connect one copper plate to a free end of the white crocodile clip wire. Connect the other copper plate to a free end of the red crocodile clip wire.
- Slice a lemon in half. Insert the copper and magnesium plates into one lemon half at a distance of about 1 cm apart from each other. Repeat with the other two plates using the other lemon half. Make sure that the plates do not touch each other.
- Take a light emitting diode. Connect a free end of the red crocodile clip wire to a long leg of the diode. Connect a free end of the black crocodile clip wire to a short leg of the diode. The diode will light up!
Disposal
Dispose of solid waste together with household garbage. Pour solutions down the sink. Wash with excess of water.
That’s interesting!
What is diode, and how does it work?
Diode is a tiny device that can conduct electricity (in one direction) and sometimes turn this energy into useful work. In our case, we will deal with a light-emitting diode (LED): it glows when passing through electrical current.
The base of all modern diodes is a semiconductor. The latter is a special material with quite poor electroconductivity that can, however, be increased – for instance, by heating. By the way, what is electroconductivity? It is ability of a material to conduct electrical current.
Interestingly, unlike a regular conductor, any diode contains two “types” of semiconductors. Even the word diode (from the Greek δίς) indicates that it comprises two elements: an anode and a cathode.
An anode in a diode is made of a semiconductor that contains so-called holes. They are the void regions that can be filled with electrons. These holes may be imagined as empty shelves designed specifically for electrons. Moreover, these “shelves” may to a certain degree freely move throughout the anode. A cathode in a diode is also made of a semiconductor. However, this second semiconductor is different: it contain excess of electrons that, again, can almost freely move throughout the cathode.
Notably, this construction of a diode allows electrons to freely pass through a diode in one direction, but prohibits their movement in the opposite direction. When electrons move from a cathode toward an anode, then on the border between these parts “free” electrons in the cathode meet with electron vacancies (“shelves”) in the anode. There, electrons gladly occupy these vacancies, allowing the current to move further. You can see this process in the video below.
Now, let’s imagine that electrons have to move in the opposite direction. They have to leave their cozy shelves and move into the material that has no shelves at all! Obviously, this way is no gain for electrons, and thus the current doesn’t flow in that direction.
Therefore, any diode may work as some sort of a check valve for electricity: it passes through a diode in one direction and cannot pass through in the opposite direction. This unique property provided for the use of diodes in electronics. Any computer, smartphone, laptop of a tablet has a processor containing millions of microscopic diode-like devices called transistors.
Light-emitting diodes, in turn, are employed in lighting and indicating. To make a diode that produces light, they thoroughly select its semiconductor components. In a certain combination of selected semiconductors, transfer of electrons from a cathode to vacancies in an anode is accompanied by emission of a photon, i.e. a portion of light. For various semiconductors, glow color is different. An important feature of diodes, in comparison with other electrical sources of light, is their safety and high efficiency, or degree of converting electrical current into light.
