Electrical circuits, elements of electrical circuits. Symbols of electric circuit elements

Electrotechnical devices are very important in the life of a modern civilized person. But for their work, a number of requirements must be met. Within the framework of the article, we will carefully consider the electrical circuits, the elements of electrical circuits and how they function.

What do you need to operate an electrical device?

For its functioning, an electric circuit must be created . Its task is to transfer energy to the device and provide the required operating mode. What is called an electrical circuit? So designate a set of objects and devices that form the path of current movement. In this case, electromagnetics processes can be described with the help of knowledge of the electric current, as well as those that offer electromotive force and voltage. It is worth noting that when speaking of such a concept as an element of an electrical circuit, the resistance in this case will play a rather significant role.

Nuances of graphic marking

To make it more convenient to analyze and calculate the electrical circuit, it is represented in the form of a circuit. It contains symbolic elements of the elements, as well as methods from the connection. In general, what is an electrical circuit in the form of a scheme, it is well understood that the photographs used in the article are understandable. Periodically you can find drawings with other schemes. Why is this so? The designations for the electrical circuit elements of the circuits created in the territory of the CIS and other countries differ slightly. This is due to the use of various graphic marking systems.
The main elements of the electrical circuit, depending on the design and role in the schemes, can be classified according to different systems. Within the framework of the article they will be considered three.

Types of elements

Conditionally they can be divided into three groups:

1. Power supplies. A feature of this type of element is that they can convert some kind of energy (most often chemical) into electrical energy. There are two types of sources: primary, when another type of electricity transforms into electrical energy, and secondary ones, which have an electrical energy at the input and output (for example, a rectifier device).
2. Consumers of energy. They convert an electric current into something else (lighting, heat).
3. Auxiliary elements. This includes various components, without which the real circuit will not work, such as switching equipment, connecting wires, measuring devices, etc., similar in purpose.

All elements are covered by one electromagnetic process.

How to interpret images in practice?

To calculate and analyze real electrical circuits, use the graphical component in the form of a circuit. In it, the placed elements are represented with the help of symbols. But here there are special features: thus, auxiliary elements are not usually indicated on the diagrams. Also, if the resistance of the connecting wires is significantly less than that of the components, it is not indicated or taken into account. The power supply is designated as EMF. If necessary, to sign each element, it is indicated that it has an internal resistance r0. But real consumers substitute their parameters R1, R2, R3, ..., Rn. Due to this parameter, the ability of the circuit element to convert (irreversibly) electricity to other types is taken into account.

Elements of the circuit of the electrical circuit

The symbols for the elements of the electrical circuit in the text version can not be represented, therefore they are depicted in the photo. But still the narrative should be. Thus, it should be noted that the elements of the electrical circuit are divided into passive and active. The first include, for example, connecting wires and electric receivers. The passive element of the electric circuit is distinguished by the fact that its presence under certain conditions can be neglected. What can not be said about its antipode. The active elements include those of them, where EMF is induced (sources, motors, accumulators, when they are charged, etc.). Important in this regard are special details of circuits that have resistance, which is characterized by current-voltage dependence, as they mutually affect each other. When the resistance is constant regardless of the current or voltage, this relationship looks like a straight line. They are called linear elements of the electrical circuit. But in most cases, the magnitude of the resistance is affected by both current and voltage. Last but not least, this is due to the temperature parameter. So, when the element is heated, the resistance begins to increase. If this parameter is in strong dependence, then the current-voltage characteristic is not the same at any point of the mental graph. Therefore, the element is called nonlinear.

As you can see, the symbols for the elements of the electrical circuit exist differently and in large numbers. Therefore, it is hardly possible to remember them at once. This will help the schematic images presented in this article.

In which modes does the electrical circuit operate?

When a different number of consumers are connected to the power supply, the values of currents, powers and voltage accordingly change. And this depends on the mode of operation of the chain, as well as the elements that it includes. The circuit of the design used in practice can be represented as an active and passive two-terminal network. So the chains that connect to the outer part (in relation to it) are called by means of two terminals, which, as you might guess, have different poles. The peculiarity of the active and passive two-terminal network consists in the following: in the first there is a source of electric energy, and in the second one it is absent. In practice, replacement schemes are widely used during the operation of active and passive elements. What will be the mode of operation is determined by the parameters of the latter (changes due to their adjustment). And now let's look at what they are.

Idling speed

It involves disconnecting the load from the power source using a special key. The current in this case becomes zero. The voltage is equalized at the terminals of the terminals to the EMF level. Elements of the circuit of the electrical circuit are not used in this case.

Short circuit mode

Under such conditions, the circuit key is closed and the resistance equals zero. Then the voltage at the terminals is also = 0. If you use both modes that have already been considered, then the parameters of the active two-terminal network can be determined from their results. If the current varies within certain limits (which depend on the part), the lower bound is always zero, and this component begins to give off the energy of the external circuit. If the indicator is less than zero, then it will be he who will give the energy. It should also be taken into account that if the voltage is less than zero, it means that the resistors of the active two-terminal network consume the energy of the sources with which there is a link due to the circuit, as well as the resources of the device itself.

Nominal mode

It is necessary to provide technical parameters for both the whole chain and individual elements. In this mode, the indicators are close to those values that are indicated on the very part, in the reference literature or technical documentation. It should be borne in mind that each device has its own parameters. But three main indicators can be found almost always - this is the rated current, power and voltage, they have all the electrical circuits. Elements of electrical circuits also all of them without exception.

Harmonized mode

It is used to provide the maximum transmission of active power that goes from the power source to the energy consumed. In this case, it will be superfluous to calculate the utility parameter. When working with this mode, it is necessary to be careful and be prepared that part of the scheme will fail (unless theoretical aspects are worked out in advance).

The main elements during the calculations for electrical circuits

They are used in complex designs to test what and how it will work:

1. Branch. This is the section of the circuit with the same current value. The branch can be completed from one / several elements, which are connected in series.
2. Node. A place where at least three branches are connected. If they are connected to one pair of nodes, they are called parallel.
3. Circuit. Similarly, any closed path that passes through several branches is called.

Here such divisions have electric circuits. Elements of electrical circuits in all cases, except for the branch, are necessarily present in the set.

Conditional positive directions

They need to be set to correctly formulate equations that describe the processes that occur. The importance of the direction is for currents, EMF power supplies, as well as voltages. Features of marking on circuits:

1. For EMF sources, they are indicated arbitrarily. But it must be taken into account that the pole to which the arrow is directed has a higher potential than the second one.
2. For currents that work with EMF sources - must coincide with them. In all other cases, the direction is arbitrary.
3. For voltages - coincides with the current.

Types of electrical circuits

How are they distinguished? If the parameters of the element are independent of the current that flows in it, then it is called linear. An example is an electric furnace. The non-linear elements of the electrical circuit have a resistance that grows when the voltage rises, which is applied to the lamp.

Laws that will be needed when working with DC circuits

Analysis and calculation will be much more effective if you simultaneously use Ohm's law, as well as the first and second laws of Kirchhoff. With their help, it is possible to establish a relationship between the values that currents, voltages, and EAF have over the entire electrical circuit or in its individual sections. And this is all based on the parameters of the elements that they contain.

Ohm's law for a chain section

For us, the current (I), voltage (U) and resistance (R) are important. This law is expressed by the following formula: I = U / R. When calculating electrical circuits, it is sometimes more convenient to use a reciprocal value: R = I / U.

Ohm's law for the complete chain

It defines the dependence that is established between the EMF (E) of the power source, whose internal resistance is equal to r, current and the general equivalent of R. The formula looks like I = E / (r + R). A complex chain has, as a rule, several branches. They can include other power sources. Then to use Ohm's law for a full description of the process becomes problematic.

The First Law of Kirchhoff

Any node of an electrical circuit has an algebraic sum of currents, which is zero. The currents that go to the node, in this case are taken with a plus sign. Those that are directed from him - with a minus. The importance of this law lies in the fact that it establishes a relationship between currents that are at different nodes.

The Second Law of Kirchhoff

The algebraic sum of the EMF in any selected closed loop is equal to the summed number of voltage drops on all its sections. Is it always so? No. If voltage sources were included in the electrical circuit, then this indicator will be zero. During the recording of the equation according to this law it is necessary:

1. Select the direction by which the contour will be traversed.
2. Set positive indices for currents, EMF and voltages.

Conclusion

So, we examined electrical circuits, electrical circuit elements and practical features of interaction with them. Despite the fact that the topic involves an explanation with simple terminology, because of its volume, it is quite difficult to understand. But, having understood it, it is possible to understand the processes taking place in the electrical circuit and the purpose of its elements.