For lovers of all kinds of experiments and experiments, we offer an unusual idea - try to build a primitive battery from sour lemons with your own hands. We spend a lot of money on batteries, accumulators to power phones, watches, toys, without thinking at all that we are surrounded by a mass of inexpensive energy sources, from which we can assemble an economical and simple galvanic cell at any time with our own hands. We do not even imagine how many interesting things surround us!
To conduct the experiment, we need, as I mentioned above, lemons (8 pieces), 9 thin wires with clips, 8 small pieces of copper wire and the same number of galvanized nails, a clock with a battery, and, of course, a voltmeter to test the possibilities ( voltage) of the battery we built.
Having lightly stretched the lemons in our hands, we stick a piece of copper wire and one galvanized nail into each of them. We take a watch, remove the battery from it, and with the help of wires we create an electrical circuit, as in the picture. We connect the free ends of the wires from the first and eighth lemons to the clock in the places where the battery was previously, creating a closed circuit. At the end of the experiment, we will see how the clock will go. By connecting the ends of the wires to a voltmeter, we can observe a voltage of 0.49 V.
It is easy to explain how our fruit battery works. When copper and zinc come into contact with citric acid, a chemical reaction occurs, as a result of which copper becomes positively charged, and zinc negatively. With a closed circuit created with copper wire and small galvanized nails, an electric current begins to act. Zinc (source of electrons) is the negative pole fruit battery, copper is positive. Battery voltage is related to the ability of zinc and copper to donate electrons. The electric current depends on the number of electrons released during the chemical reaction being run.
If there are no lemons at home, any other citrus fruits, kiwi, bananas, apples, pears, potatoes, tomatoes, cucumbers, onions can be used as the main material for the experiment. These vegetables and fruits can also work as a battery, although their voltage will be slightly different from a lemon current source. The pear will give the highest voltage, the kiwi will give the lowest. The electrical characteristics of the created batteries are affected by the acidity of the products used. By connecting several fruit batteries in series, we will achieve an increase in voltage in proportion to the amount of fruit used.
A pair of copper and zinc can be replaced with other components, for example, copper and aluminum, aluminum and zinc. True, in the latter case, the battery will turn out to be somewhat weaker than the "original" lemon one.
The above experiment is a direct confirmation that a person can freely use natural renewable materials to meet their energy needs. A number of companies on an industrial scale have already begun to create unusual batteries using processed bananas and orange peels. The Sony company recently presented to the public a battery in which fruit juice is used instead of an electrolyte. By filling the battery with 8 ml of juice, you can power small portable electronics for one hour. Scientists from the UK have created a similar version of the battery for a low-power computer with an Intel 386 processor. It has been experimentally proven that 12 potatoes can become a full-fledged source of energy for a computer within 12 days.
Light a light bulb with... a lemon!
Complexity:
Danger:
Before starting the experiment, put on protective gloves and goggles.
Do the experiment on a tray.
General safety rules
First Aid Information
First, make sure that the plates in the lemon do not touch each other.
Secondly, check the quality of the connection of crocodiles with metal plates.
Thirdly, make sure that the LED is connected correctly: the black crocodile is attached to the short “leg”, the red one to the long one. In this case, the crocodiles should not touch the other “leg”, otherwise the circuit will close!
Everything is fine. Magnesium is an active metal and reacts with citric acid to form magnesium citrate and release hydrogen.
Dispose of the solid waste of the experiment with household waste. Drain the solutions into the sink and then rinse thoroughly with water.
Under the conditions of the experiment, a chemical reaction occurs: electrons from magnesium Mg are transferred to copper Cu. This movement of electrons is an electric current. Passing through the LED, it causes it to glow. Thus, the installation assembled in this experiment acts as a battery - a chemical source of current.
To learn more
The participants in this experiment - copper Cu and magnesium Mg - are very similar. Both are metals. This means that they are quite malleable, shiny, conduct electricity and heat well. All these properties are consequences of the internal structure of metals. It can be thought of as positive ions arranged in a certain order, which are held together with the help of electrons common to the entire piece of metal. It is because of this commonality that electrons can “walk” throughout the entire volume of the metal.
Despite the common motifs in the structure, copper and magnesium differ from each other. The total "pack" of electrons is held in a piece of copper more strongly than in the case of magnesium. Therefore, purely theoretically, we can imagine a process in which electrons from magnesium "run away" to copper. However, this will lead to an increase in charges: positive in magnesium and negative in copper. This cannot continue for a long time: due to mutual repulsion, it will be unprofitable for negatively charged electrons to move further into copper. The charge is thus collected at the contact surface of two different metals.
Curiously, the degree of electron transfer from one metal to another depends on temperature. This connection is used in electronic devices that measure temperature. The simplest such device that uses this effect is thermocouple. Now the use of thermocouples is ubiquitous, and they are the basis of electronic thermometers.
Let's go back to our experience. In order for electrons to constantly run from magnesium to copper, and the process itself to become irreversible, it is necessary to remove the positive charge from magnesium and the negative charge from copper. This is where lemon comes into play. It is important what kind of environment it creates for the copper and magnesium plates stuck into it. Everyone knows that lemon has a sour taste mainly due to the citric acid contained in it. Naturally, there is also water in it. A solution of citric acid is capable of conducting electricity: when it dissociates, positively charged hydrogen ions H + and a negatively charged citric acid residue appear. Such an environment is ideal for removing the positive charge from magnesium and the negative charge from copper. The first process is quite simple: positively charged magnesium ions Mg 2+ pass from the surface of the magnesium plate into a solution (lemon juice):
Mg 0 - 2e - → Mg 2+ solution
The second process takes place on a copper plate. Since a negative charge accumulates on it, this attracts hydrogen ions H +. They are able to take electrons from a copper plate, turning first into H atoms, and then almost immediately into H 2 molecules, which fly away:
2H + + 2e - → H 2
The closest analogue of the "copper plate - lemon - magnesium plate" system is an ordinary finger battery. It works on the same principle: the chemical reactions occurring inside it lead to the emergence of a current of electrons, that is, electricity. You probably noticed that in some devices, finger-type batteries are arranged in a row (that is, the negative pole of one is in contact with the positive pole of the other). More often they do this not directly, but through wires or small metal plates. But the essence remains the same - this is necessary to increase the force that acts on the electrons, which means to increase the current strength.
Similarly, a copper plate in one piece of lemon is connected to a magnesium plate in another. If you connect a diode with only one copper-magnesium pair, it will not glow, but using two pairs leads to the desired result.
To learn more
To describe the force that makes charges move, that is, leads to the appearance of electricity, use the concept voltage. For example, any battery indicates the voltage value that it can create in a device or conductor connected to it.
The voltage that one magnesium-copper pair creates is not enough for this experiment, but two pairs are already enough.
All metals have different ability to hold electrons. This allows them to be arranged in the so-called electrochemical series. Metals that are to the left of this row retain electrons worse, and those to the right are better. In our experience, the electric current arises precisely from the difference between copper and magnesium in their ability to hold electrons. In the electrochemical series, copper is much to the right of magnesium.
We may well take the other two metals, it is only necessary that there be a sufficient difference between their desire to keep electrons with them. For example, in this experiment, silver Ag can be used instead of copper, and zinc Zn can be used instead of magnesium.
However, we chose magnesium and copper. Why?
Firstly, they are very affordable, unlike the same silver. Secondly, magnesium is a metal that simultaneously combines sufficient activity and stability. Like alkali metals - sodium Na, potassium K and lithium Li - it is easily oxidized, that is, it gives up electrons. On the other hand, the surface of magnesium is covered with a thin film of its oxide MgO, which is not destroyed when heated up to 600 o C. It protects the metal from further oxidation in air, which makes it very convenient to use in practice.
Many fruits and vegetables will be suitable for this experience. It is enough that they have juicy pulp. For example, instead of lemon, you can take an apple, banana, tomato or potato. Even a large grape will do!
In all these vegetables, fruits and berries there is enough water, as well as substances that dissociate (decompose into charged particles - ions) in water. Therefore, electric current can also flow in them!
Diodes are small devices capable of passing an electric current through themselves and doing some useful work. In this case, we are talking about an LED - when an electric current is passed, it glows.
All modern diodes are based on a semiconductor - a special material whose electrical conductivity is not very high, but can grow, for example, when heated. What is electrical conductivity? This is the ability of a material to conduct an electric current through itself.
Unlike a simple piece of semiconductor, any diode contains two of its "grades". The very name "diode" (from the Greek "δίς") means that it contains two elements - they are usually called anode and cathode.
The anode of a diode consists of a semiconductor containing so-called "holes" - areas that can be filled with electrons (actually empty shelves especially for electrons). These "shelves" can move quite freely throughout the anode. The cathode of the diode also consists of a semiconductor, but a different one. It contains electrons, which can also move relatively freely through it.
It turns out that such a composition of the diode allows electrons to easily move through the diode in one direction, but practically does not allow them to move in the opposite direction. When electrons move from the cathode to the anode, at the boundary between them there is a meeting of "free" electrons in the cathode and electron vacancies (shelves) in the anode. Electrons gladly occupy these vacancies, and the current moves on.
Imagine that the electrons are moving in the opposite direction - they need to get off the cozy shelves into the material where these shelves are not! Obviously, this is not beneficial for them and the current will not go in this direction.
So any diode can act as a sort of valve for electricity to flow through it one way but not the other. It is this property of diodes that made it possible to use them as the basis for computer technology - any computer, smartphone, laptop or tablet contains a processor based on millions of microscopic diodes.
LEDs, of course, have another application - in lighting and indication. The very fact of the appearance of light is associated with a special selection of semiconductor materials that make up the diode. In some cases, the same transition of electrons from the cathode to anode vacancies is accompanied by the release of light. In the cases of different semiconductors, the glow of different colors occurs. Important advantages of diodes over other electric light sources are their safety and high efficiency - the degree of conversion of electric current energy into light.
It happens that you find yourself in a difficult life situation when you urgently need a source of energy. For example, you need to charge your mobile phone, turn on the radio, and so on. Elementary knowledge of physics and chemistry will allow you to find a way out of such situations. For many, it will be interesting to know that you can “power up” a radio or charge a mobile phone from an apple or a lemon.
For these purposes you will need:
- steel contact (nail, paper clip, piece of steel wire, steel coin and so on...);
- copper contact (copper coin, piece of copper wire, any copper plate, etc.);
- lemon, and if an apple is used, you need to choose as sour as possible;
- two wires for connecting to the "battery".
Procedure:
Stage 1. Looking for a suitable "energy source"
The easiest way is to find an apple when you are in a country house, village, or simply lost in the forest. The best option would be a sour apple, since acid is a key component in the work of the "battery". If there is a lemon, then this is the most suitable option. You can also use oranges, kiwi and other similar fruits.
Stage 2. We establish contacts
You need to insert contacts into a lemon or an apple, first they need to be thoroughly cleaned with sandpaper, a file, or rubbed against a stone. Contacts are inserted at a distance of 2-3 centimeters from each other. The wider and longer the inserted electrodes, the more voltage the battery will produce. If coins act as contacts, then they must be inserted in parallel.
Stage 3. We connect the battery
Now it remains to connect two wires to the established contacts. You can simply gently stick them into a lemon or apple along with the contacts. That's it, the battery is ready to use. There will be a plus on the copper electrode, and a minus on the steel. The voltage will depend on the area of the electrodes and the acidity of the apple or lemon.
Stage 4. Charging lemons
An interesting fact is that the "batteries" created in this way can be fully charged. For these purposes, you can use a charger from a mobile phone. The author decided to use a Krona battery for these purposes.
The red positive wire is connected to the copper electrode, and the black negative wire to the steel one. After charging, a voltage of 1-1.3 Volts will appear on the contacts of the "lemon".
Many schoolchildren in the lessons of chemistry, physics or labor were lucky enough to make a battery out of a lemon. It sounds strange, because everyone is used to seeing standard-type batteries. But the source of energy from the fruit is something unusual!
In fact, you can build such an installation from any fruit. The only difference will be in tension. Lemon has the advantage of having citric acid. It is capable of generating more electrical current.
Here's what you need to create a lemon battery:
As you can see, there are only three things at the heart of the manufacture of this battery.
Step #1.
Take a lemon and remember it a little. You can also wash and dry if you wish. Although it's not that important.
Step #2.
Place a copper conductor at a shallow depth of up to 2 cm and a metal conductor not far from it.
Connect wires to protruding twigs.
Test with a multimeter how many volts this installation produces.
As a result, 0.91 volts!
Collect the second lemon battery and connect them in series. Or stick another copper and metal wire. Then diagonally connect them together.
The fact is that the LED will not burn from one battery, so a second one is required.
Thus, a lemon battery can stably produce an electric current.
Explanation: The operation of such a battery is based on the interaction of two conductors of opposite metals. After they are placed in a lemon, they are surrounded by a medium of citric acid. This substance serves as an electrolyte. That is, a chemical reaction begins to flow and the ions move, giving out energy.
In place of the coin, it is best to use copper wire.
