Direct current is the orderly unidirectional movement of charges in a conductor. The speed is subject to change. From this current to be constant does not stop. In technology, it is customary to attribute the unipolar sequence of pulses. For example, it is believed that the current after the rectifier bridge is constant. In reality, it is a unipolar pulse train.
The Origin of Electricity
The history of electricity was considered in the subject of AC, but details remained. Daughters of Thales of Miletus world owes knowledge of electricity. The word comes from the ancient Greek name of amber, and the first seriously engaged in the research of William Gilbert. By that time, Peregrin’s work on magnetism — the only short manuscript — was already known, and the physicist knew about Thales of Miletus from Aristotle’s treatises.
The release of the book De magnete, magneticisque corparibus etc was in 1600.To better understand the situation, recall that after 9 years of investigation in the specified period Giordano Bruno was burned. Without spilling blood, as required by the rules of the Inquisition. Former priest at the denunciation of his friend went to the fire. After 5 years, the Powder plot occurred under King Jacob I.The court accused a group of Catholics in an attempt to blow up parliament and even caught Guy Fawkes.
That sad autumn nobles, contrary to the established traditions, were tortured on the rack. Guy did not give up, but when colleagues began to sign testimony, he did the same. The handwriting was very different from the usual - it is impossible to write with mutilated hands. Guy was helped to execution on the gallows by the executioners, but he managed to deftly jump and break his neck, avoiding further painful procedures.
William Gilbert, who did not live to the Powder Conspiracy for a couple of years, and who passed away with assumption of the throne, Jacob I, released this treatise in connection with indescribable mysterious phenomena, electricity and magnetism. Describes that shabby amber deflects the compass needle aside, constructs a device, called a versor, for observation and experimentation. Scientists could easily be accused of witchcraft - the Inquisition and a similar kind of structure burned witches. This affected mainly the mainland of Europe, but it was also hot in England. The law on the cessation of prosecution for witchcraft was released in Great Britain only in 1735.
Before constant electricity could well cause, if not execution, then unpleasant procedures. So, Gilbert, plucking up courage, says that electricity is considered a weak force, easily destroyed. It is only necessary to place a dielectric between the bodies, as the effect of attraction is disturbed. At the same time, magnetism is recognized as a strong feature and does not depend on the ingress of moisture, the influence of objects and other things. Elected bodies can electrify, but others do not. Magnetism affects only selected materials, and a “weak” phenomenon affects everything( according to Gilbert).Other characteristics are noted. For example, the magnet is characterized by constancy, and to electrify the body should be rubbed to "shine, heat or expiration."
The book is full of technical errors due to the imperfection of research methods. But this gave scientists an exodus, and two hundred years later Volta's pole was invented. This is a constant voltage source, a bit like a modern battery. Not bad, if we consider that 20 Thousands( 2000 years) passed after Thales of Miletus, while the person decided to present a scientifically simple phenomenon of the electrification of amber. The relay was taken over by Nikola Cabo, who in the Philosophy of Magnetism( 1629) tried, while avoiding souls from material bodies, to explain mysterious phenomena. For reasons of the scientist, a thing endowed with unusual qualities, pushing and squeezing the air, why the observed phenomena occurred. It was suggested that there is no difference between ordinary and charged bodies in a thousand-fold experiments on permanent objects.
Father of DC is called Otto von Guericke, who listened to Gilbert with diligence. The scientist wanted to create a machine that automates the process of friction, and gradually came to the design of the first static generator. For these purposes, Guericke recommends using a ball of sulfur the size of a child's head. The accumulated electrical potential was amazing, the scientist immediately makes a number of discoveries:
- Charges are able to attract and repel.
- Electricity flows through conductors.
The reaction of the scientific world was absent. No one noticed the outstanding discoveries against the background of the works of Gerika on the topic of rarefied gases. Systematized information on electricity by Charles Dyufe in December 1733, many years after the death of an outstanding scientist. The experimenter found that the charges are of two characters, the first immediately dubbed glass, the second - resin. After a couple of years, European states begin to part with the practice of persecuting citizens for witchcraft, discoveries follow each other.
Formation of the concept of direct current
With the growth of those wishing to engage in electricity, there are more people eager for fame. For example, the following messages were registered:
- Chicken eggs hatch faster from electrified chicken eggs.
- Similar experiments performed on seeds gave an accelerated development of crops.
- Electricity revives dead animals.
Suppose that some of the facts described are not entirely true. In 1940, a group of Soviet physiologists showed that under the action of artificial blood supply, the heart and lungs, the head and the whole animal( dog) come to life. It remains to be wondered why the technology has not received further development.
Let's return to electricity: in 1745, a leyden bank was invented - the first capacitor in the world capable of storing a charge. The plates were tin sheets, dielectric - glass. You can’t pass by John Canton, who has greatly improved the version of Gilbert. The new device was called an electroscope, it showed the interaction of charges and their approximate quantitative assessment. The device consisted of a small wood ball, on a silk thread suspended from a hook. When you bring a charged body, the effect of electrostatic polarization manifested itself, the object attracted a load.
In the following, a wooden bead was replaced with a material capable of accepting a charge, trying to determine the sign. John Canton is still considered the discoverer of electrostatic induction, explained by Epinus on the basis of the theory of long-range action, and Charles Coulon takes over the baton. In 1784, a physicist armed with the knowledge of previous generations using torsional weights defines his own famous law. For the first time, a direct current of chemical nature was supposed to be obtained in 1791 by Galvani, but the discovery did not occur due to the prevailing circumstances. The scientist was engaged in physiology:
- A prepared dead frog began to twitch under the touch of metal hooks. This is the usual equipment for vivisectors, just a miracle that the effect was noticed.
- Repeating experiments on dielectrics, Galvani found that the effect was never observed.
From the work done, the scientist made the wrong conclusion about the presence of animal electricity. Here the great Alessandro Volta took up the work. It is not known how many frogs tortured the husband of science, but the conclusion is amazing: electricity, or more precisely, direct current appears when metals interact with different characteristics through an electrolyte - the liquid of a dead creature. In the spring of 1800, the world's first source, called the Voltaic Pillar, appeared. This is an electrochemical device, where the zinc and copper plates are immersed in the electrolyte.
The discovery originally lay in the field of physiology; saline water became the conductive fluid. It is recommended to be used instead of blood even in emergency situations. Then Wollaston replaced salt water with acid. These discoveries, like a nuclear reactor, energized the researchers. The discoveries began to grow like mushrooms after a warm autumn rain: electrolysis, incandescent lamps, an electric motor, Ohm's law for a complete circuit, first opened for direct current.
Direct current in the modern world
So, it took 200 years for humanity to come from simple experiments on electrifying bodies to direct current. After another 200, on November 20, the first Pentium IV processor came to light. A good jerk. The processor is also powered by direct current, as a system unit as a whole. The consumption of the electronic brain is up to 70 watts. When powered from a source with a voltage of 3 V, the current is more than 20 A. Today it is known that the processor has enough contacts, and the resulting current is really large, but it is divided into many branches. It is no wonder that for such units they produce coolers of 50 W or more( power of the average incandescent bulb).
So, the direct current prevails in electronics. Depending on the chip family used, the polarity is positive and negative. That is why the power ratings are numerous. From DC, stepper motors are powered in a hard disk or drive for reading optical media, providing better efficiency.
Direct current is widely used in batteries, can be stored in contrast to AC.Rather, voltage is stored, but in the considered context we will consider the terms as synonyms: charge and discharge are a direct current. Before the era of Nikola Tesla, no alternating current was used, engines and other equipment needed constant generators.
Direct current is often used in sensors, sometimes in the form of pulses. It is difficult to understand when the voltage changes. But the direction is unchanged - it means everything is correct. This is how Hall sensors work. Thermocouple in this role is considered, rather, a device operating on voltage, a constant current given by this source is very small.