Once on a desert island, modern Robinson could indulge in the pleasure of using a player, smartphone or pocket flashlight, provided that he could extract electricity from coconuts and bananas.
Surely many of the physics course remember or have heard that from ordinary potatoes, and not only from them, you can get some electricity.
What is needed for this, and is it possible in this way to light a low-power flashlight, an LED clock powered by round batteries of 1-2 Volts, or make a radio receiver work?
And yes and no, let's take a closer look.
To understand that the voltage from a potato is not a fiction, but a very real thing, it is enough to stick sharp probes from a multimeter into one single potato and you will immediately see several millivolts on the screen.
If you complicate the structure a little, for example, insert a copper electrode or a bronze coin into the tuber on one side, and something aluminum or galvanized on the other side, then the voltage level will increase significantly.
Potato juice contains dissolved salts and acids, which are essentially a natural electrolyte.
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By the way, lemons, oranges, apples can be used with equal success. Thus, all these products can feed not only people, but also electrical appliances.
Inside such fruits and vegetables, due to oxidation, electrons will escape from the submerged anode (galvanized contact). And they will be attracted to another contact - copper. However, do not be confused, electricity is not generated directly from potatoes here. It is well produced precisely due to the chemical processes between the three elements:
- zinc
- copper
- acid
And it is the zinc contact that serves as a consumable here. All electrons flow away from it. Under certain conditions, even earthen soil can provide electricity. The main condition is its acidity.
Earthen battery
The increased acidity of the soil is a problem for agronomists, but a joy for electrical engineers. The content of hydrogen and aluminum ions in the earth allows you to literally stick two sticks (as usual, zinc and copper) into the pot and get electricity. Our result is 0.2 V. To improve the result, the soil should be watered.
It is important to understand that electricity is not generated from lemon or potatoes. This is not at all the energy of chemical bonds in organic molecules, which is absorbed by our body as a result of food consumption. Electricity is generated by chemical reactions involving zinc, copper and acid, and in our battery it is the nail that serves as a consumable.
Assembling a battery from potatoes
So, here's what you need to assemble a more or less capacitive battery:
Potatoes, several pieces, since one will be of little use.
Copper, preferably single-core wires, the larger the cross-section, the better.
Galvanized and copper nails or screws (just wire can be used).
Nails will play a major role in generating electricity for the flashlight, galvanized nails are a negative contact (anode), copper-plated nails are a plus (cathode).
If you use simple nails instead of galvanized ones, then you will lose up to 40-50% in tension. But as an option, it will still work.
The same applies to the use of aluminum wire instead of nails. At the same time, an increase in the distance between the electrodes in one potato does not play a special role.
Take copper wires (mono core) with a cross section of 1.5-2.5mm2, 10-15cm long. Strip them from insulation and tie them to a carnation.
It is best of course to solder, then the voltage loss will be much less.
One copper nail on one side of the wire and galvanized on the other.
Next, lay out the potatoes and consistently stick nails into them. In this case, different nails are stuck into each tuber, from different pairs of wires. That is, you should have one zinc contact and one copper contact in each potato.
Different tubers are connected to each other, only through nails made of different materials - copper + zinc - copper + zinc, etc.
Voltage measurements
Let's say you have three potatoes, and you connected them together as described above. To find out what the voltage is, use a multimeter.
Switch it to the DC voltage measurement mode and connect the measuring probes to the conductors of the extreme potatoes, i.e. to the initial positive contact (copper) and the final negative contact (zinc).
Even three medium-sized potatoes can produce almost 1.5 Volts.
If, however, reduce all transition resistances to the maximum, and for this:
- use not a nail as a copper electrode, but the very wire that the circuit is assembled with
- use soldering in contacts
then only 4 potatoes are capable of producing up to 12 volts!
If your cheap flashlight is powered by three AA batteries, then you will need about 5 volts to glow successfully. That is, when using ordinary wires, you need at least three times more potatoes.
For this, by the way, it is not necessary to look for additional tubers, it is enough to cut the existing ones into several parts with a knife. Then do the same procedure with wires and studs.
Insert one galvanized and one copper stud into each cut tuber. As a result, it is quite possible to get a constant voltage of more than 5.5V.
Is it possible, theoretically, to get 5 volts from a single potato and at the same time ensure that the entire assembly is no larger than a finger battery in size? It is possible and very easy.
Cut off small pieces of the core from the potatoes, and place them between flat electrodes, for example, coins of different metals (bronze, zinc, aluminum).
In the end, you should end up with something like a sandwich. Even one piece of such an assembly is capable of delivering up to 0.5V!
And if you collect several of them together, then the required value up to 5V will easily be obtained at the output.
Current strength
It would seem that everything, the goal has been achieved, and it remains only to find a way to connect the wiring to the power contacts of the flashlight or LEDs.
However, having done this procedure and having assembled a not weak construction of several cards, you will be very disappointed with the final result.
Low-power LEDs of course will glow, after all, you still received voltage. However, the brightness level of their glow will be catastrophically dim. Why is this happening?
Because, unfortunately, such a galvanic cell gives a negligible current. It will be so small that not even all multimeters can measure it.
Someone will think, since there is not enough current, you need to add more potatoes and everything will work out.
Of course, a significant increase in tubers will increase the working voltage.
When dozens and hundreds of potatoes are connected in series, the voltage will increase, but the most important thing will not be - sufficient capacity to increase the current strength.
And all this design will not be rationally suitable.
The practical way with boiled potatoes
But still, is there a simple way to increase the power of such a battery and reduce its size? Yes there is.
For example, if for this purpose you use not raw, but boiled potatoes, then the power of such a source of electricity increases several times!
Use an old C (R14) or D (R20) battery for a convenient compact design.
Remove all the contents inside (of course, except for the graphite rod).
Instead of filling, fill the entire space with boiled potatoes.
Then assemble the battery in reverse order.
The zinc part of the old battery case plays an essential role here.
The total area of the inner walls is much larger than just stuck carnations into raw potatoes.
Hence the high power and efficiency.
One such power supply would easily deliver nearly 1.5 volts, as would a small AA battery.
But the most important thing for us is not volts, but milliamps. So, such a "boiled" upgrade is capable of providing a current of up to 80mA.
These batteries can power a receiver or an electronic LED clock.
Moreover, the entire assembly will work not for seconds, but for several minutes (up to ten). More batteries and potatoes, more battery life.
Lemon battery
Acetic battery. An ice cube tray can help you design a multi-cell battery with vinegar as the electrolyte. Use galvanized screws and copper wire as electrodes. After filling the battery with vinegar and connecting an LED lamp to it, try gradually filling up and stirring table salt in the cells: the brightness of the glow will grow before our eyes.
Juicy fruits, young potatoes and other foods can serve as food not only for people, but also for electrical appliances. To get electricity from them, you need a galvanized nail or screw (that is, almost any nail or screw) and a piece of copper wire. To record the presence of electricity, a household multimeter will come in handy, and an LED lamp or even a fan powered by batteries will help to more clearly demonstrate success.
Mash the lemon in your hands to break down the internal partitions, but do not damage the rind. Insert the nail (screw) and copper wire so that the electrodes are as close to each other as possible, but not touching. The closer the electrodes are, the less likely they are to be separated by a partition inside the fruit. In turn, the better the ion exchange between the electrodes inside the battery, the greater its power.
The essence of the experiment was to place the copper and zinc electrodes in an acidic environment, be it a lemon or a vinegar bath. The nail will serve as a negative electrode, or anode. The copper wire is designated as a positive electrode, or cathode.
In an acidic environment, an oxidation reaction occurs on the anode surface, during which free electrons are released. Each zinc atom leaves two electrons. Copper is a strong oxidizing agent and it can attract electrons released by zinc. If you close an electrical circuit (connect a light bulb or a multimeter to an improvised battery), electrons will flow from the anode to the cathode through it, that is, electricity will appear in the circuit.
