Constant electric current is the movement of particles with a charge in a certain direction. That is, its voltage or force (characterizing quantities) have the same meaning and direction. This is how direct current differs from alternating current. But consider everything in order.
The history of the emergence and “current war”
Direct current was previously called galvanic due to the fact that it was discovered as a result of a galvanic reaction. Thomas Edison tried to transmit it through electric transmission lines. At that time there were serious disputes between scientists on this issue. They even got the name "current war". The question of the choice as the main, variable or permanent. The “fight” was won by a variable view, since the constant one incurs significant losses, transmitted from a distance. But transforming an alternating view is not difficult, this is how direct current differs from alternating. Therefore, the latter is easy to transmit even over great distances.
Sources of direct current
The sources may be batteries or other devices where it occurs through a chemical reaction.
These are generators, where it is obtained as a result of electromagnetic induction, and after that it is rectified by the collector.
Application
In various devices, direct current is used quite often. For example, many household appliances, chargers and car generators work with it. Any portable device is powered from a source that produces a constant look.
On an industrial scale, it is used in engines and batteries. And in some countries they are equipped with high-voltage power lines.
In medicine, with the help of direct electric current, wellness procedures are carried out.
On the railway (for transport), both variable and constant types are used.
Alternating current
Most often, however, they use it. Here, the average value of force and tension for a certain period is equal to zero. In size and direction, it is constantly changing, and with equal intervals of time.
To induce alternating current, generators are used in which an electromotive force occurs during electromagnetic induction . This is carried out using a magnet rotated in a cylinder (rotor), and a stator made in the form of a fixed core with a winding.
Alternating current is used in radio, television, telephony and many other systems due to the fact that its voltage and power can be converted, almost without losing energy.
It is widely used in industry, as well as for lighting purposes.
It can be single-phase and multiphase.
Alternating current, which varies according to the sinusoidal law, is single-phase. It changes over a certain period of time (period) in magnitude and direction. AC frequency is the number of periods per second.
In the second case, the three-phase version is most widespread. This is a system of three electric circuits that have the same frequency and EMF, phase shifted by 120 degrees. It is used to power electric motors, furnaces, and lighting fixtures.
Many developments in the field of electricity and their practical application, as well as exposure to high frequency alternating current, mankind owes to the great scientist Nicola Tesla. Until now, not all of his works left to posterity are known.
How is direct current different from alternating current and what is its path from source to consumer?
So, a variable is called a current that can change in direction and magnitude over a certain time. The parameters that are paid attention to are the frequency and voltage. In Russia, in household electrical networks they supply alternating current having a voltage of 220 V and a frequency of 50 Hz. The frequency of alternating current is the number of changes in the direction of particles of a certain charge per second. It turns out that at 50 Hz it changes its direction fifty times, in which direct current differs from alternating current.
Its source is sockets, to which household appliances are connected under different voltages.
Alternating current begins its movement from power plants, where there are powerful generators, where it comes from with a voltage of 220 to 330 kV. Then it goes to transformer substations, which are located near houses, enterprises and other structures.
In the substation, the current gets under a voltage of 10 kV. There, it is converted to a three-phase voltage of 380 V. Sometimes, with such an indicator, the current passes directly to the objects (where powerful production is organized). But basically it is reduced to the usual 220 V in all houses.
Conversion
It is clear that in sockets we get alternating current. But often a constant look is needed for electrical appliances. For this purpose, special rectifiers are used. The process consists of the following actions:
- connecting a bridge with four diodes having the required power;
- connecting a filter or capacitor to the output from the bridge;
- connecting voltage stabilizers to reduce ripple.
Conversion can occur both from AC to DC, and vice versa. But the latter case will be much more difficult to implement. Inverters are needed, which, among other things, are quite expensive.