In contact with
Classmates
The first was invented by accident, at the end of the 17th century, by the Italian scientist Luigi Galvani. In fact, the goal of Galvani's research was not at all to search for new sources of energy, but to study the reaction of experimental animals to various external influences. In particular, the phenomenon of the appearance and flow of current was discovered when strips of two different metals were attached to the muscle of the frog's leg. The theoretical explanation for the observed process Galvani developed incorrectly, but his experiments became the basis for the research of another Italian scientist Alessandro Volta, who actually formulated the main idea of the invention - the cause of the electric current is a chemical reaction in which metal plates take part. To confirm his theory, Volt created a simple device that consisted of zinc and copper plates immersed in a container of saline. It was this device that became the world's first autonomous battery and the progenitor of modern batteries, which are called galvanic cells in honor of Luigi Galvani.
Modern autonomous power sources have little in common with the device created by Alessandro Volta, but the basic principle has remained unchanged. Any battery consists of three main elements - two electrodes, called an anode and a cathode, and an electrolyte located between them. The occurrence of an electric current is a by-product of the redox reaction between the electrodes. The output current, voltage and other parameters of the battery depend on the selected materials of the anode, cathode and electrolyte, as well as the design of the battery itself. All batteries can be divided into two large classes - primary and secondary. In primary batteries, chemical reactions are irreversible, while in secondary batteries they are reversible. Accordingly, secondary elements, which we know as, can be restored (charged) and reused.
The beginning of the industrial production of primary chemical current sources was laid in 1865 by the Frenchman J. L. Leklanshe, who proposed a manganese-zinc cell with a salt electrolyte. In 1880, F. Laland created a manganese-zinc cell with a thickened electrolyte. Subsequently, this element has been significantly improved. A significant improvement in performance was obtained by using electrolytic manganese dioxide at the cathode and zinc chloride in the electrolyte. Until 1940, the manganese-zinc salt element was practically the only primary chemical current source used. Despite the appearance in the future of other primary current sources with higher characteristics, the manganese-zinc salt cell is used on a very large scale, largely due to its relatively low price.
One of the most important factors in the development of batteries (as well as any device powered by them) is to achieve the maximum specific capacity for a cell of a given (minimum) size and weight. The chemical reactions that take place inside an element determine both its capacity and its physical dimensions. In principle, the whole history of battery development comes down to finding new chemical systems and packing them into packages as small as possible.
Today, many different types of batteries are produced, some of which were developed as early as the 19th century, while others have barely celebrated a decade. This diversity is explained by the fact that each technology has its own strengths. We will talk about the most common of those used in mobile devices.
Dry batteries
The first mass-produced batteries were dry ones. The heirs of Leclanche's invention, they are the most common in the world. Energizer alone sells over 6 billion of these batteries annually. In general, "we say a battery, we mean a dry cell." And this, despite the fact that they have the lowest specific capacity of all "mass" types. Such popularity is explained, firstly, by their cheapness, and secondly, by the fact that three different chemical systems are called by this name at once: chlorine-zinc, alkaline and manganese-zinc batteries (Leclanchet elements). Their names give an idea of the chemical systems on which they are based.
In dry cells, a carbon rod of the cathode current collector is located along the axis. The cathode itself is a whole system, which includes manganese dioxide, electrode carbon and electrolyte. The zinc "cup" serves as the anode and forms the metal body of the cell. The electrolyte, in turn, is also a mixture that includes ammonia, manganese dioxide and zinc chloride.
Manganese-zinc and zinc-chlorine cells differ, in fact, in electrolyte. The former contain a mixture of ammonia and zinc chloride, diluted with water. In zinc-chlorine electrolyte almost 100% is zinc chloride. The difference in their nominal voltage is minimal: 1.55V and 1.6V, respectively.
Despite the fact that zinc chloride cells have a higher capacity than Leclanche cells, this advantage disappears at low load. Therefore, they are often written "heavy-duty", that is, elements with increased power. Be that as it may, the efficiency of all dry cells drops dramatically with increasing load. That is why you should not put them in modern cameras, they are simply not designed for this.
No matter how many pink bunnies run in advertising, alkaline batteries are still the same coal-zinc fossils from the 19th century. The only difference lies in the specially selected electrolyte mixture, which allows to achieve an increase in the capacity and shelf life of such batteries. What's the secret? This mixture is somewhat more alkaline than the other two types.
If the chemical composition of alkaline batteries differs little from that of the Leclanche element, then the differences in design are significant. We can say that an alkaline battery is a dry cell turned inside out. Their outer case is not an anode, it is just a protective shell. The anode here is a jelly-like mixture of zinc powder mixed with an electrolyte (which in turn is an aqueous solution of potassium hydroxide). The cathode, a mixture of carbon and manganese dioxide, surrounds the anode and electrolyte. It is separated by a layer of non-woven material such as polyester.
Depending on the application, alkaline batteries can last up to 4-5 times longer than conventional zinc-carbon batteries. This difference is especially noticeable in this mode of use, when short periods of high load are punctuated by long periods of inactivity.
It is important to remember that alkaline batteries are not rechargeable because the chemistry they are based on is not reversible. If you put it in a charger, then it will not behave like a battery, but rather like a resistor - it will start to heat up. If it is not removed from there in time, it will heat up strongly enough to explode.
The name tells us that this type of battery has a nickel anode and a cadmium cathode. Nickel-cadmium batteries (designated Ni-Cad) are well-deservedly popular with consumers around the world. Last but not least, this is due to the fact that they withstand a large number of charge-discharge cycles - 500 and even 1000 - without a significant deterioration in performance. In addition, they are relatively light and energy-intensive (although their specific capacity is about half that of alkaline batteries). On the other hand, they contain toxic cadmium, so you need to be careful with them, both during use and after disposal.
The output voltage of most batteries drops as they are discharged because their internal resistance increases as a result of chemical reactions. Nickel-cadmium batteries are characterized by very low internal resistance, and therefore they can supply a fairly high current to the output, which, moreover, practically does not change as they are discharged. Accordingly, the output voltage also remains almost unchanged until the charge almost completely dries up. Then the output voltage drops sharply to almost zero.
A constant output voltage level is an advantage when designing electrical circuits, but it also makes determining the current charge level almost impossible. Due to this feature, the remaining energy is calculated based on the operating time and the known capacity of a particular type of battery, and therefore is an approximate value.
A much more serious disadvantage is the "memory effect". If such a battery is not completely discharged, and then put on charge, then their capacity may decrease. The fact is that with such an "incorrect" charging, cadmium crystals are formed on the anode. They play the role of the chemical "memory" of the battery, remembering this intermediate level. When the battery drops to this level during the next discharge, the output voltage will drop in the same way as if the battery were completely discharged. Rancorous crystals will continue to form at the anode, amplifying this nasty effect. To get rid of it, you need to continue discharging after reaching this intermediate level. This is the only way to "erase" the memory and restore the full capacity of the battery.
This technique is commonly referred to as deep discharge. But deep does not mean full, "to zero". This will only harm and shorten the life of the element. If, during use, the output voltage drops below 1 Volt (at a nominal voltage of 1.2 V), then this can already lead to battery damage. Sophisticated appliances, such as PDAs or laptops, are configured to turn off before the battery drops below the limit. For deep discharge of batteries, you need to use special devices that are produced by many well-known companies.
Some manufacturers claim that new nickel-cadmium batteries are not affected by the memory effect. However, this has not been proven in practice.
Whatever the manufacturers promise, in order to achieve maximum efficiency, the batteries should be fully charged each time, and then wait for normal discharge so that they do not deteriorate and last the entire period.
To partially eliminate the shortcomings of nickel-cadmium batteries, nickel-metal hydride (Ni-MH) batteries were called upon, in which there was no "dangerous" cadmium. Just like nickel-cadmium batteries, nickel-metal hydride batteries have a nickel anode, but the cathodes were made from hydrides, which are actually metal alloys that can hold atomic hydrogen. Nickel-metal hydride batteries have a much weaker memory effect, they have a better ratio of capacity and overall dimensions. However, nickel-metal hydride batteries can withstand fewer charge-discharge cycles and are more expensive than nickel-cadmium batteries. Also, a problem for nickel-metal hydride batteries was a large self-discharge value - for a day, without load, batteries of this type managed to lose up to 5% of their capacity.
Most batteries in the world are lead. They are mainly used to start car engines. The prototype of these elements was the development of Plante. They also have anodes made of cellular lead and cathodes made of lead oxide. Both electrodes are immersed in an electrolyte - sulfuric acid.
Because of the lead, these batteries are very heavy. And since they are flooded with highly corrosive acid (which also makes batteries heavier), they also become dangerous, requiring special attention. Acid and fumes can damage nearby objects (especially metal). And if you overdo it with charging, electrolysis of the water in the acid may begin. This produces hydrogen, an explosive gas that, under certain conditions, can explode (as in the case of the Hindenburg explosions).
The decomposition of water in the battery can lead to another effect: after all, the total amount of water in the battery decreases. At the same time, the reaction area inside the battery decreases, and the battery capacity decreases accordingly. In addition, the reduction of liquid allows the battery to be discharged by exposure to the atmosphere. The electrodes can peel off and short out the battery altogether.
The first lead batteries required regular maintenance - it was necessary to maintain the right level of water / acid inside each cell. Since only water undergoes electrolysis in the battery, only water needs to be replaced. To avoid battery contamination, manufacturers recommend that only distilled water be used for maintenance. Usually the battery is topped up to a normal level. If there is no mark on the battery, it must be topped up so that the liquid covers the electrode plates inside.
In fixed devices, the battery case is made of glass. It not only holds acid well, but also allows maintenance personnel to determine the condition of the elements without much difficulty. In automotive technology, stronger housings are required. Engineers for these purposes used ebonite or plastic.
After the cells began to be sealed, the convenience of using such lead-acid batteries became invaluable. As a result, so-called maintenance-free batteries appeared. Since the vapor remains inside the cells, electrolysis losses are minimized. Therefore, such batteries do not require refueling with water (at least they should not).
But this does not mean that such batteries do not have maintenance problems at all. There is still acid sloshing around inside. And that acid can leak out through the battery valves. This may damage the battery compartments or even the equipment where it is installed. Engineers avoid this situation in two ways. It is possible to contain the acid inside a plastic separator between the cell electrodes (usually made of microporous polyolefin or polyethylene). Or you can mix the electrolyte with another substance to form a gel—for example, a colloidal mass like gelatin. As a result, no leakage occurs.
In addition to the dangerous stuffing, lead batteries have other disadvantages. As noted above, they are very heavy. The amount of energy that is contained in a unit mass of such batteries is less than in batteries of almost any other technology. This is the only thing that car makers are not satisfied with, who would love to use these inexpensive lead batteries in electric cars.
On the other hand, although these batteries are cheap, they have a history of 150 years. The technology allows batteries to be upgraded for special needs, such as for use in devices with long discharge cycles (where batteries are used as the only source of power) or in uninterruptible power applications, such as in large data centers. Lead batteries also have low internal resistance and can therefore generate very high currents. Unlike more exotic elements, such as nickel-cadmium, they are not subject to the memory effect. (This effect, in the case of nickel-cadmium cells, reduces the capacity of the battery if it is recharged before it is completely discharged.) In addition, such batteries have a long life and are predictable. And, of course, they are cheap.
Most of these sources use lead batteries with a jelly-like electrolyte. Usually, such devices are unpretentious in maintenance. This means that you do not think about their maintenance. The power supplies, however, are rather bulky, because the batteries are inside. When fully charged, jelly-like cells gradually deteriorate under the influence of a constant low-current charge. (Most lead-acid batteries are kept fully charged.) Therefore, such cells require special chargers that would automatically turn off as soon as the cell is fully charged. The charger should turn on again as soon as the battery is discharged to a predetermined level (whether under load or self-discharge). Normally, uninterruptible power supplies regularly check the battery charge.
Electrolysis Prevention
As in lead batteries, electrolysis is possible in nickel-cadmium batteries - the breakdown of water in the electrolyte into potentially explosive hydrogen and oxygen. Battery manufacturers take various measures to prevent this effect. Typically, elements are hermetically sealed to prevent leakage. In addition, the batteries are designed so that oxygen is not produced first, but oxygen, which prevents the electrolysis reaction.
In order to prevent sealed batteries from exploding, and so that gas does not accumulate in them, valves are usually provided in the batteries. If these ventilation openings are blocked, there is a risk of explosion. Usually these holes are so small that they go unnoticed. They work automatically. This warning (do not cover the ventilation openings) applies mainly to device manufacturers. Standard battery compartments allow ventilation, but if you fill the battery in epoxy, there will be no ventilation.
Lithium is the most reactive metal and is used in the smallest systems that power the most advanced mobile technology. Lithium cathodes are used in almost all high capacity batteries. But due to the activity of this metal, the batteries are not only very capacious, they also have the highest nominal voltage. Depending on the anode, lithium-containing cells have an output voltage of 1.5 V to 3.6 V!
The main problem with the use of lithium, again, is its high activity. It can even flash - let alone not the nicest feature when it comes to batteries. Because of these problems, lithium metal cells, which began to appear as early as the 70s and 80s of the 20th century, became famous for their low reliability.
To get around these difficulties, battery manufacturers have tried to use lithium in the form of ions. Thus, they managed to get all the useful electrochemical qualities without messing with the capricious metal form.
In lithium-ion cells, lithium ions are bound by molecules of other materials. A typical Li-Ion battery has a carbon anode and a lithium cobalt dioxide cathode. The electrolyte is based on a solution of lithium salts.
Lithium batteries are denser than nickel-metal hydride batteries. For example, in laptops, such batteries can work one and a half times longer than nickel-metal hydride ones. In addition, lithium-ion cells are spared the memory effects that plagued early nickel-cadmium batteries.
On the other hand, the internal resistance of modern lithium cells is higher than that of nickel-cadmium cells. Accordingly, they cannot provide such strong currents. If nickel-cadmium cells are capable of melting a coin, then lithium ones are not capable of it. But all the same, the power of such batteries is quite enough to operate a laptop, if it is not associated with intermittent loads (this means that some devices, for example, a hard drive or CD-ROM, should not cause high surges in extreme modes - for example, during initial spin-up or wake up from sleep mode). What's more, even though lithium-ion batteries can last hundreds of charges, they last less than those that use nickel.
Due to the fact that lithium-ion cells use a liquid electrolyte (even if separated by a layer of tissue), they are almost always cylindrical in shape. Although this form is no worse than the forms of other cells, with the advent of polymerized electrolytes, lithium-ion batteries are becoming more compact.
The most advanced battery technology used today is lithium polymer. Already now, among manufacturers, both batteries and computer devices, there has been a trend towards a gradual transition to this type of cells. The main advantage of lithium polymer batteries is the absence of a liquid electrolyte. No, this does not mean that scientists have found a way to do without electrolyte at all. The anode is separated from the cathode by a polymer baffle, a composite material such as polyacrylonitrite that contains a lithium salt.
Due to the absence of liquid components, lithium-polymer cells can take almost any shape, unlike other types of cylindrical batteries. The usual forms of packaging for them are flat plates or bars. In this form, they better fill the space of the battery compartment. As a result, for the same specific gravity, optimally shaped lithium polymer batteries can store 22% more energy than comparable lithium ion batteries. This is achieved by filling the "dead" volumes in the corners of the compartment, which would remain unused in the case of a cylindrical battery.
In addition to these obvious advantages, lithium polymer cells are environmentally friendly and lighter, due to the absence of an external metal case.
Lithium iron disulfide batteries
Unlike other lithium-containing batteries, which have an output voltage of more than 3V, lithium-iron disulfide has half that. Also, they cannot be recharged. This technology is a compromise that developers have made to ensure the compatibility of lithium power supplies with technology designed to use alkaline batteries.
The chemical composition of the batteries has been specially modified. In them, the lithium anode is separated from the iron disulfide cathode by an electrolyte layer. This sandwich is packaged in a sealed case with microvalves for ventilation, just like nickel-cadmium batteries.
This type of cell was conceived as a competitor to alkaline batteries. Compared to them, lithium-iron disulfide ones weigh a third less, have a larger capacity, and, in addition, they also last longer. Even after ten years of storage, they retain almost all of their charge.
The superiority over competitors is shown in the best way at the big loading. In the case of high load currents, lithium iron disulfide cells can last up to 2.5 times longer than alkaline batteries of the same size. If the output does not require high current, then this difference is much less noticeable. For example, one battery manufacturer claims the following characteristics for two types of its AA batteries: at 20 mA, an alkaline battery will last 122 hours versus 135 hours for a lithium iron disulfide battery. If the load is increased to 1A, then the duration of work will be 0.8 and 2.1 hours, respectively. As they say, the result is obvious.
It makes no sense to put such powerful batteries in devices that consume relatively little energy for a long time. They were specially designed for use in cameras, powerful flashlights, and it is better to put alkaline batteries in an alarm clock or radio receiver.
Charging technologies
Modern chargers are fairly sophisticated electronic devices with varying degrees of protection for both yours and your batteries. In most cases, each cell type has its own charger. If the charger is used incorrectly, not only the batteries, but also the device itself, or even systems powered by batteries, can be damaged.
There are two modes of operation of chargers - with constant voltage and with constant current.
The simplest are devices with constant voltage. They always produce the same voltage, and supply a current that depends on the battery level (and other environmental factors). As the battery charges, its voltage increases, so the difference between the potentials of the charger and the battery decreases. As a result, less current flows through the circuit.
All that is needed for such a device is a transformer (to reduce the charging voltage to the level required by the battery) and a rectifier (to rectify AC to DC used to charge the battery). Such simple recharging devices are used to charge car and ship batteries.
As a rule, lead batteries for uninterruptible power supplies are charged by similar devices. In addition, constant voltage devices are also used to recharge lithium-ion cells. Only there are added circuits to protect the batteries and their owners.
The second type of charger provides a constant current and changes the voltage to provide the required amount of current. Once the voltage reaches the full charge level, charging stops. (Remember, the voltage created by the cell drops as it discharges.) Typically, such devices charge nickel-cadmium and nickel-metal hydride cells.
In addition to the desired voltage level, you must know how long it takes to recharge the element. The battery can be damaged if you charge it for too long. Depending on the type of battery and on the "intelligence" of the charger, several technologies are used to determine the recharge time.
In the simplest cases, this uses the voltage generated by the battery. The charger monitors the battery voltage and turns off when the battery voltage reaches a threshold level. But this technology is not suitable for all elements. For example, for nickel-cadmium it is not acceptable. In these elements, the discharge curve is close to a straight line, and it can be very difficult to determine the threshold voltage level.
More "sophisticated" chargers determine the recharge time by temperature. That is, the device monitors the temperature of the cell, and turns off, or reduces the charge current when the battery starts to heat up (which means overcharging). Usually, thermometers are built into such batteries, which monitor the temperature of the element and transmit the corresponding signal to the charger.
"Smart" devices use both of these methods. They can go from high charge current to low charge current, or they can maintain a constant current using special voltage and temperature sensors.
Standard chargers give less charge current than the cell's discharge current. And chargers with a large current value give more current than the rated discharge current of the battery. A trickle charge device uses a current so small that it almost does not allow the battery to self-discharge (by definition, such devices are used to compensate for self-discharge). Typically, the charge current in such devices is one-twentieth or one-thirtieth of the battery's rated discharge current. Modern chargers can often handle multiple charge currents. They use higher currents at first and gradually switch to lower currents as they approach full charge. If you use a battery that can withstand trickle charging (nickel-cadmium, for example, do not), then at the end of the recharge cycle, the device will switch to this mode. Most laptop and cell phone chargers are designed to be permanently plugged into the cells without harming them.
Battery history.
If we trace the history of batteries, it is obvious that Alessendro Volta was the first to take a step towards their creation, but he did not guess how to make the galvanic cell he received rechargeable. Another German scientist, Wilhelm Zinsteden, observed the effect of obtaining direct current by immersing lead plates in sulfuric acid, but did not draw conclusions from this that can be applied in practice.
We owe the creation of the battery to the French. It was the French scientist Gaston Plant who created in 1859 his prototype - a lead-acid battery, which, unlike galvanic, could be recharged.
The American inventor of the light bulb, Thomas Edison, became interested in the properties of a rechargeable battery. He was the first to come up with the idea of using batteries for the needs of transport and contributed to the start of the production of car batteries. Edison was not only a great scientist, but also a practical thinker. Thanks to him, electricity really became at the service of mankind.
.jpg)
Since then, the essence of the energy storage process in a lead-acid battery has not changed at all, only the materials used in its production have changed. Old ebonite battery cases have been replaced by modern polypropylene ones. Ebonite is less impact-resistant material, besides polypropylene is much cheaper.
Modern car battery.
A modern car battery is the old lattice porous lead plates (one is lead, the other is lead dioxide), dipped into an electrolyte prepared from a mixture of distilled water and sulfuric acid with many additives that improve its properties. But the latest technologies used in the manufacture of automotive batteries significantly improve their performance. They reduce corrosion, increase the service life of batteries, improve the reception and return of electric charge, reduce water loss and shedding of the active mass, increase the temperature regime by increasing frost resistance. Some additional devices, such as indicators, allow you to monitor the degree of charge of the battery.
The most important advantage of modern batteries can be called an increase in the values of the starter current, which ensures a stable engine start in any temperature conditions, and a longer service life due to a decrease in self-discharge.
The first experiments that showed the ability to accumulate, i.e. to accumulate electrical energy, were produced shortly after the discovery by the Italian scientist Volta of the phenomena of galvanic electricity.
In 1801, the French physicist Gautero, passing a current through water through platinum electrodes, discovered that after the current was interrupted through the water, it was possible, by connecting the electrodes to each other, to obtain a short-term electric current.
The scientist Ritter then did the same experiment, using instead of platinum electrodes electrodes made of gold, silver, copper, etc., and separating them from each other with pieces of cloth soaked in salt solutions, he obtained the first secondary, i.e., capable of giving away stored in him electrical energy, an element.
The first attempts to create a theory of such an element were made by Volta, Marianini and Bequerel, who argued that the action of the battery depends on the decomposition of salt solutions into acid and alkali by electric current, and that these latter then, when combined, again give an electric current.
This theory was defeated in 1926 by the experiments of Deryariva, who was the first to use acidified water in a battery.
Acidified water during the passage of the current decomposes, obviously, into oxygen and hydrogen, and the element owes its subsequent action to this decomposition. Grove brilliantly proved this position by building his famous gas accumulator, consisting of plates lowered into acidified water and surrounded in the upper part: one with hydrogen and the other with oxygen. However, an accumulator in this form was very impractical, since in order to store large quantities of electricity, it was necessary to store a very large amount of gases, which occupied a large volume.
A great practical improvement in the development of accumulators was introduced in 1859 by Gaston Plante, who, as a result of a long series of experiments, came to a type of accumulator consisting of lead plates with a large surface, which, when charged with current, were covered with lead oxide, a. releasing oxygen and liquid, they gave off an electric current.
Plante took two strips of sheet lead, laid strips of cloth between them, and folded the strips around a round stick. Then he tightened the resulting bundle with rubber rings and put it in a vessel with acidified water. With repeated charging and discharging of such a battery, an active active layer was formed on the surface of the plates, which participated in the process and gave the element a large capacity. However, the need for a very large number of charges and discharges of the Plante battery to give it some capacity greatly increased the cost of the battery and made it difficult to produce it.
The next improvement that brought the battery to its modern form was the use in 1880 by Camille Faure of lattice lead plates, the cells of the lattices of which were stuffed with a specially prepared mass, made in advance. This process greatly simplified and reduced the cost of manufacturing batteries, reducing battery molding to a very short process.
Further improvements in the history of lead-acid batteries were already on the way to improving the method of filling and molding the lattice plates used by Fore, without making drastic changes to the design of the battery. In parallel with the development of lead-acid batteries, which have a number of major and unrecoverable shortcomings, such as a large weight per unit capacity, the impossibility of being stored without damage in a discharged state, etc., there was a development of applications for the manufacture of batteries and other metals, except for lead.
School scientific and practical conference
youth and schoolchildren
"Search. The science. Opening."
the city of Novocheboksarsk
Nikolaev Alexander
student of class 5A MOU "Secondary School No. 13"
the city of Novocheboksarsk
Scientific adviser:
Komissarova Natalya Ivanovna,
physics teacher, MOU "Secondary School No. 13"
Novocheboksarsk, 2011
2. The history of the battery…..……………………………………………………… 3-5
3. Battery device .. ………………………………………………………………… 5
4. Experiment…………………………………………………………………………… 5
5. On the use of fruits and vegetables to generate electricity. ................ 7
6. Conclusions…………………………………………………………………………………... 8
7. Used literature………………………………………………………….. 8
Introduction
Our work is devoted to unusual sources of energy.
Chemical current sources play a very important role in the world around us. They are used in mobile phones and spacecraft, cruise missiles and laptops, cars, flashlights and ordinary toys. We deal with batteries, accumulators, fuel cells every day.
For the first time, we read about the non-traditional use of fruits in the book of Nikolai Nosov. As conceived by the writer, Shorty Vintik and Shpuntik, who lived in the Flower City, created a car that runs on soda with syrup. And then we thought, what if vegetables and fruits keep some more secrets. As a result, we wanted to learn as much as possible about the unusual properties of vegetables and fruits.
The aim of our work is the study of the electrical properties of fruits and vegetables.
We have set ourselves the following tasks:
1 Get to know the battery device and its inventors.
2. Find out what processes take place inside the battery.
3.Experimentally determine the voltage inside the "tasty" battery and the current generated by it.
4. Assemble a circuit consisting of several of these batteries and try to light a light bulb.
5. Find out if vegetable and fruit batteries are used in practice.
The history of the battery
The first chemical source of electric current was invented by accident, at the end of the 17th century, by the Italian scientist Luigi Galvani. In fact, the goal of Galvani's research was not at all to search for new sources of energy, but to study the reaction of experimental animals to various external influences. In particular, the phenomenon of the appearance and flow of current was discovered when strips of two different metals were attached to the muscle of the frog's leg. Galvani's theoretical explanation for the observed process was incorrect.
Galvani's experiments became the basis for the research of another Italian scientist, Alessandro Volta. He formulated the main idea of the invention. The cause of the electric current is a chemical reaction in which metal plates take part. To confirm his theory, Volta created a simple device. It consisted of zinc and copper plates immersed in a container of brine. As a result, the zinc plate (cathode) began to dissolve, and gas bubbles appeared on the copper steel (anode). Volta suggested and proved that electric current flows through the wire. Somewhat later, the scientist assembled a whole battery of series-connected elements, thanks to which it was possible to significantly increase the output voltage.
It was this device that became the world's first battery and the progenitor of modern batteries. And batteries in honor of Luigi Galvani are now called galvanic cells.
Just a year after that, in 1803, the Russian physicist Vasily Petrov assembled the most powerful chemical battery, consisting of 4,200 copper and zinc electrodes, to demonstrate an electric arc. The output voltage of this monster reached 2500 volts. However, there was nothing fundamentally new in this “voltaic column”.
In 1836, the English chemist John Daniel improved the Volta element by placing zinc and copper electrodes in a solution of sulfuric acid. This design became known as the "Daniel element".
In 1859, the French physicist Gaston Plante invented the lead-acid battery. This type of cell is still used in car batteries to this day.
The beginning of the industrial production of primary chemical current sources was laid in 1865 by the Frenchman J. L. Leklanshe, who proposed a manganese-zinc cell with a salt electrolyte.
In 1890, in New York, Konrad Hubert, an immigrant from Russia, creates the first pocket electric flashlight. And already in 1896, the National Carbon company began mass production of the world's first dry elements Leklanshe "Columbia". The longest-lived galvanic cell is a zinc-sulfur battery made in London in 1840.
Until 1940, the manganese-zinc salt element was practically the only chemical current source used.
Despite the appearance in the future of other primary current sources with higher characteristics, the manganese-zinc salt cell is used on a very large scale, largely due to its relatively low price.
In modern chemical current sources are used:
as a reducing agent (at the anode) - lead Pb, cadmium Cd, zinc Zn and other metals;
as an oxidizing agent (at the cathode) - lead (IV) oxide PbO2, nickel hydroxide NiOOH, manganese (IV) oxide MnO2 and others;
as an electrolyte - solutions of alkalis, acids or salts.
Battery device
Modern galvanic cells outwardly have little in common with the device created by Alessandro Volta, but the basic principle has remained unchanged. Batteries produce and store electricity. There are three main parts inside the dry cell that powers the appliance. This is a negative electrode (-), a positive electrode (+) and an electrolyte located between them, which is a mixture of chemicals. Chemical reactions cause electrons to flow from the negative electrode through the instrument and then back to the positive electrode. Thanks to this, the device works. As the chemicals are used up, the battery runs out.
The battery case, which is made of zinc, can be covered with cardboard or plastic on the outside. Inside the case are chemicals in the form of a paste, and some batteries have a carbon rod in the middle. If the power of the battery drops, it means that the chemicals have been used up and the battery is no longer able to produce electricity.
Recharging such batteries is impossible or very irrational (for example, to charge some types of batteries, you will have to spend tens of times more energy than they can store, while other types can accumulate only a small part of their initial charge). After that, the battery will only have to be thrown into the trash.
Most modern batteries were developed already in the 20th century in the laboratories of large companies or universities.
experimental part
Scientists say that if the electricity goes out in your house, you can light up your house with lemons for a while. Indeed, in any fruit and vegetable there is electricity, because they charge us, people, with energy when they are consumed.
But we are not accustomed to taking everyone's word for it, so we decided to test it in experience. So, to create a "tasty" battery, we took:
lemon, apple, onion, raw and boiled potatoes;
a few copper plates from the electrostatics kit - this will be our positive pole;
galvanized plates from the same set - to create a negative pole;
wires, clamps;
millivoltmeters, voltmeters
ammeters.
a light bulb on a stand, rated for a voltage of 2.5 V and a current of 0.16A.
We entered the results of the experiment in the table.
Conclusion: the voltage between the electrodes is approximately the same. And the magnitude of the current is probably related to the acidity of the product. The greater the acidity, the greater the current strength.
If you use not raw, but boiled potatoes, then the power of the device will increase by 4 times.
We decided to investigate how voltage and current depend on the distance between the electrodes. To do this, they took a boiled potato, changed the distance between the anode and the cathode, and measured the voltage and current on the battery. The results of the experiment were entered into the table.
|
Distance between electrodes, cm |
Voltage between electrodes, V |
Short circuit current, mA |
|
1 |
0,6 |
2,1 |
|
2,5 |
0,7 |
3,6 |
|
3,5 |
0,7 |
3,8 |
|
5 |
0,8 |
4,2 |
Conclusion: the voltage between the electrodes and the current strength increase with increasing distance between them. The short circuit current is small, because the internal resistance of the potato is great.
Next, we decided to make a battery of two, three, four potatoes. Having previously increased the distance between the electrodes to the maximum, the potatoes were successively included in the circuit. The results of the experiment were entered into the table.
Conclusion: the voltage at the battery terminals increases and the current decreases. The current is too low to light the bulb.
Therefore, we plan to further find out in what ways it is possible to increase the current strength in the circuit and make the light bulb glow.
We have been watching our "delicious" batteries for some time. The results of the measured voltage on the batteries were entered in the table:
Conclusion: gradually the voltage on all the "tasty" batteries decreases. So far there is still strain on apple, onion and boiled potatoes.
Pulling out copper and zinc plates from fruits and vegetables, we noticed that they were heavily oxidized. This means that the acid reacted with zinc and copper. Due to this chemical reaction, a very weak electric current flowed.
About using fruits and vegetables to generate electricity.
Recently, Israeli scientists have invented a new source of clean electricity. As an energy source for an unusual battery, the researchers proposed using boiled potatoes, since the power of the device in this case will increase by 10 times compared to raw potatoes. Such unusual batteries can last for several days or even weeks, and the electricity they generate is 5-50 times cheaper than that obtained from traditional batteries and at least six times more economical than a kerosene lamp when used for lighting.
Indian scientists have decided to use fruits, vegetables and their waste to power simple household appliances. The batteries contain a paste made from recycled bananas, orange peels and other vegetables or fruits inside, in which zinc and copper electrodes are placed. The novelty is designed primarily for residents of rural areas, who can prepare their own fruit and vegetable ingredients to recharge unusual batteries.
Conclusions:
1 We got acquainted with the battery device and its inventors.
2. We learned what processes take place inside the battery.
3. Made vegetable and fruit batteries
4. We learned to determine the voltage inside the “tasty” battery and the current strength created by it.
5. We noticed that the voltage between the electrodes and the current strength increase with increasing distance between them. The short circuit current is small, because the internal resistance of the battery is high.
6. We found that the voltage at the terminals of a battery made up of several vegetables is growing, and the current is decreasing. The current is too low to light the bulb.
7. In the assembled circuit, the light bulb could not be lit, because current is small.
References:
1 Encyclopedic Dictionary of a Young Physicist. -M.: Pedagogy, 1991
2 O. F. Kabardin. Reference materials on physics.-M.: Education 1985.
3 Encyclopedic Dictionary of a Young Technician. -M.: Pedagogy, 1980.
4 Journal "Science and Life", No. 10, 2004.
5 A. K. Kikoin, I.K. Kikoin. Electrodynamics.-M.: Nauka 1976.
6 Kirilova I. G. A book for reading in physics. - Moscow: Education 1986.
7 Journal "Science and Life", No. 11, 2005.
8 N.V. Gulia. Amazing physics. - Moscow: "Publishing house of NTs ENAS" 2005
Internet resource.
Modern life passes under the sign of electricity, which is everywhere. It's scary to even think what will happen if all the electrical appliances suddenly disappear or fail. Power plants of various types, scattered around the world, regularly supply current to electrical networks that power appliances in production and at home. However, a person is arranged in such a way that he is never satisfied with what he has. Being tied with a wire to an electrical outlet is too inconvenient. Salvation in this situation are devices that supply electric flashlights, mobile phones, cameras and other devices that are used far from the source of electricity. Even small children know their name is batteries.
Strictly speaking, the common name "battery" is not entirely correct. It combines several types of electricity sources at once, designed for autonomous power supply of the device. This can be a single galvanic cell, a battery, or a combination of several such cells into a battery to increase the voltage removed. It was this connection that gave rise to the name familiar to our ear.
Batteries and galvanic cells, and accumulators are a chemical source of electric current. The first such source was invented, as is often the case in science, accidentally by the Italian physician and physiologist Luigi Galvani at the end of the 18th century.
Although electricity as a phenomenon has been known to mankind since ancient times, for many centuries these observations had no practical application. Only in 1600, the English physicist William Gilbert published the scientific work “On the Magnet, Magnetic Bodies and the Great Earth Magnet”, where the data on electricity and magnetism known at that time were summarized, and in 1650 Otto von Guericke created an electrostatic machine, which was a sulfur ball mounted on a metal rod. A century later, the Dutchman Pieter van Muschenbroek for the first time managed to accumulate a small amount of electricity using the "Leyden jar" of the first capacitor. However, it was too small for serious experiments. Scientists such as Benjamin Franklin, Georg Richman, John Walsh were engaged in research on "natural" electricity. It was the work of the latter on electric rays that interested Galvani.
The real purpose of the famous experiment of Galvani, who revolutionized physiology and forever inscribed his name in science, now no one will remember. Galvani dissected the frog and placed it on the table where the electrostatic machine stood. His assistant accidentally touched the open femoral nerve of the frog with the tip of a scalpel, and the dead muscle suddenly contracted. Another assistant noticed that this only happens when a spark is removed from the machine.
Inspired by the discovery, Galvani began methodically to investigate the discovered phenomenon - the ability of a dead drug to demonstrate vital contractions under the influence of electricity. After a whole series of experiments, Galvani obtained a particularly interesting result by using copper hooks and a silver plate. If the hook holding the foot touched the plate, the foot, touching the plate, immediately contracted and rose. Having lost contact with the plate, the muscles of the foot immediately relaxed, it again fell on the plate, contracted again and rose.
Luigi Galvani. Magazine illustration. France. 1880
So, as a result of a series of painstaking experiments, a new source of electricity was discovered. Galvani himself, however, did not think that the reason for the phenomenon he discovered was the contact of dissimilar metals. In his opinion, the muscle itself served as a source of current, which was excited by the action of the brain transmitted through the nerves. Galvani's discovery caused a sensation and led to many experiments in various branches of science. Among the followers of the Italian physiologist was his compatriot physicist Alessandro Volta.
In 1800, Volta not only gave a correct explanation of the phenomenon discovered by Galvani, but also designed a device that became the world's first artificial chemical source of electric current, the progenitor of all modern batteries. It consisted of two electrodes, an anode containing an oxidizing agent and a cathode containing a reducing agent, in contact with an electrolyte (salt, acid, or alkali solution). The potential difference between the electrodes corresponded in this case to the free energy of the redox reaction (electrolysis), during which electrolyte cations (positively charged ions) are reduced and anions (negatively charged ions) are oxidized at the corresponding electrodes. The reaction can start only if the electrodes are connected by an external circuit (Volta connected them with an ordinary wire), along which free electrons pass from the cathode to the anode, thus creating a discharge current. And although modern batteries have little in common with Volta's device, the principle of their operation remains the same: these are two electrodes immersed in an electrolyte solution and connected by an external circuit.
The invention of Volta gave a significant impetus to research related to electricity. In the same year, scientists William Nicholson and Anthony Carlyle decomposed water into hydrogen and oxygen using electrolysis, a little later Humphry Davy discovered potassium metal in the same way.
Galvani's experiments with a frog. Engraving from 1793
But first of all, galvanic cells are undoubtedly the most important source of electric current. Since the middle of the 19th century, when the first electrical appliances appeared, the mass production of chemical batteries began.
All these elements can be divided into two main types: primary, in which the chemical reaction is irreversible, and secondary, which can be recharged.
What we used to call a battery is a primary chemical current source, in other words, a non-rechargeable element. The first batteries launched into mass production were manganese-zinc batteries invented in 1865 by the Frenchman Georges Leclanchet with salt, and then with a thickened electrolyte. Until the early 1940s, this was practically the only type of galvanic cells used, which, due to its low cost, is still widely used. These batteries are called dry or carbon-zinc cells.
A giant electric battery designed by W. Wollaston for X. Davy's experiments.
Scheme of operation of an artificial chemical current source A. Volta.
In 1803, Vasily Petrov created the most powerful voltaic column in the world using 4200 metal circles. He managed to develop a voltage of 2500 volts, as well as to discover such an important phenomenon as an electric arc, which was later used in electric welding, as well as for electric ignition of explosives.
But the real technological breakthrough was the advent of alkaline batteries. Although their chemical composition does not differ much from Leclanchet elements, and their nominal voltage is slightly increased compared to dry cells, due to a fundamental change in the design, alkaline cells can last four to five times longer than dry ones, however, subject to certain conditions.
The most important task in the development of batteries is to increase the specific capacity of the cell while reducing its size and weight. To this end, the search for new chemical systems is constantly underway. The most high-tech primary cells today are lithium. Their capacity is twice that of dry cells, and the service life is much longer. In addition, while dry and alkaline batteries discharge gradually, lithium batteries hold voltage for almost their entire life and only then abruptly lose it. But even the best battery cannot match the efficiency of a rechargeable battery, which is based on the reversibility of a chemical reaction.
The possibility of creating such a device began to be thought about in the 19th century. In 1859 the Frenchman Gaston Plante invented the lead-acid battery. The electric current in it arises as a result of the reactions of lead and lead dioxide in a sulfuric acid environment. During current generation, the battery being discharged consumes sulfuric acid, forming lead sulfate and water. To charge it, it is necessary to pass the current received from another source through the circuit in the opposite direction, while the water will be used to form sulfuric acid with the release of lead and lead dioxide.
Despite the fact that the principle of operation of such a battery was described a long time ago, its mass production began only in the 20th century, since high voltage current is required to recharge the device, as well as compliance with a number of other conditions. With the development of electrical networks, lead-acid batteries have become indispensable and are still used in cars, trolleybuses, trams and other means of electric transport, as well as for emergency power supply.
Many small household appliances also run on "refillable batteries," rechargeable batteries that are the same shape as non-renewable galvanic cells. The development of electronics directly depends on advances in this area.
Battery J. Leclanchet.
Dry battery.
Mobile phone, digital camera, navigator, mobile computer and other similar devices in the XXI century. you won’t surprise anyone, but their appearance became possible only with the invention of high-quality compact batteries, the capacity and service life of which are being increased every year.
Nickel-cadmium and nickel-metal hydride batteries were the first to replace galvanic cells. Their significant drawback was the "memory effect" - a decrease in capacity, if charging was carried out with an incompletely discharged battery. In addition, they gradually lost their charge even in the absence of a load. These problems have largely been addressed in the development of lithium-ion and lithium-polymer batteries, which are now ubiquitous in mobile devices. Their capacity is much higher, they charge without loss at any time and hold the charge well in the standby state.
A few years ago, rumors leaked to the media that American scientists came close to inventing a "perpetual battery" of a betavoltaic cell, the energy source of which is radioactive isotopes that emit beta particles. It is assumed that such a source of energy will allow a mobile phone or laptop to work without recharging for up to 30 years. Moreover, at the end of its service life, the non-toxic and non-radioactive battery will remain absolutely safe. The appearance of this miracle device, which would no doubt revolutionize the industry, would hit the pockets of traditional battery manufacturers very hard, perhaps that is why it is still not on the shelves.
Modern device for charging rechargeable AA cells.
