Electrical devices are very important in the life of a modern civilized person. But for their work it is necessary to comply with a number of requirements. As part of the article, we will carefully consider electrical circuits, elements of electrical circuits and how they function.
What is needed for the operation of an electrical device?
For its functioning, an electrical circuit must be created . Its task is to transfer energy to the device and provide the required mode of operation. What is called an electrical circuit?
So designate a set of objects and devices that form the path of current flow. In this case, electromagnetic processes can be described using knowledge of electric current, as well as those that offer
electromotive force and voltage. It is worth noting that, speaking of such a concept as an element of an electric circuit, resistance in this case will play a rather significant role.
The nuances of graphic marking
In order to more conveniently analyze and calculate the electrical circuit, it is depicted in the form of a diagram. It contains the conventions of the elements, as well as methods from the compound. In general, what constitutes an electric circuit in the form of a circuit makes it well understood that the photographs used in the article. Periodically, you can find drawings with other schemes. Why is this so? The designations of the elements of the electric circuit of circuits created in the CIS and other countries are slightly different. This is due to the use of various graphic marking systems.
The main elements of the electric circuit, depending on the design and role in the circuits, can be classified according to different systems. In the framework of the article, three of them will be considered.
Types of Elements
Conventionally, they can be divided into three groups:
- Power supplies. A feature of this type of element is that they can turn some kind of energy (most often chemical) into electrical energy. Two types of sources are distinguished: primary, when another type is converted into electrical energy, and secondary, which have electrical energy at the input and output (an example is a rectifier device).
- Energy consumers. They convert electric current into something else (lighting, heat).
- Auxiliary elements. This includes various components without which the real circuit will not work, such as switching equipment, connecting wires, measuring instruments, 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 graphic component in the form of a diagram. In it, placed elements are depicted using symbols. But there are some peculiarities: for example, auxiliary elements are usually not indicated on the diagrams. Also, if the resistance of the connecting wires is much less than that of the components, then it is not indicated and not taken into account. The power source is referred to as EMF. If necessary, sign each element, it is indicated that it has an internal resistance r0. But real consumers substitute their parameters R1, R2, R3, ..., Rn. Thanks to this parameter, the ability of a circuit element to convert (irreversibly) electricity to other forms is taken into account.
Circuit Elements
Symbols of electric circuit elements in the text version cannot be presented, therefore they are depicted in the photo. But still the narrative should be. So, it should be noted that the elements of the electric circuit are divided into passive and active. The first include, for example, connecting wires and power consumers.
The passive element of the electric circuit is characterized in that its presence under certain conditions can be neglected. What can not be said about his antipode. Active elements include those where EMF is induced (sources, electric motors, batteries, when they are charged, and so on). Important in this regard are the special details of the circuits that have resistance, which is characterized by a current-voltage dependence, since they mutually affect each other. When the resistance is constant regardless of the current or voltage, then this dependence looks like a straight segment. They are called linear elements of the electric 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 highly dependent, then the current-voltage characteristic is not the same at any point in the mental graph. Therefore, the element is called non-linear.
As you can see, the conventions of the elements of the electric circuit are different and in large numbers. Therefore, remembering them immediately is unlikely to succeed. This will help the schematic images presented in this article.
In what modes does the electric circuit work?
When a different number of consumers are connected to the power source, the values of currents, capacities and voltage accordingly change.
And the mode of operation of the circuit, as well as the elements that enter it, depends on this. The scheme of the construction used in practice can be represented as an active and passive two-terminal device. So called chains that are connected to the external part (with respect to it) with the help of two conclusions, which, as you might guess, have different poles. The peculiarity of the active and passive bipolar consists in the following: in the first there is a
source of electrical energy, and in the second it is absent. In practice, equivalent circuits are widely used during operation of active and passive elements. The mode of operation will be determined by the parameters of the latter (changes due to their adjustment). Now let's look at what they are.
Idle mode
It involves disconnecting the load from the power source using a special key. The current in this case becomes equal to zero. The voltage is equalized in the places of the clamps to the EMF level. Elements of the circuit circuit in this case are not used.
Short circuit mode
Under these conditions, the circuit key is closed, and the resistance is 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 bipolar can be determined from their results. If the current varies within certain limits (which depend on the part), then the lower boundary is always zero, and this component begins to give off energy to the external circuit. If the indicator is less than zero, then he will give energy. It is also necessary to take into account that if the voltage is less than zero, this means that the resistors of the active two-terminal device consume the energy of sources with which there is a connection due to the circuit, as well as the reserves of the device itself.
Rated mode
It is necessary to ensure the technical parameters of both the entire circuit and individual elements. In this mode, the indicators are close to those values that are indicated on the part itself, in the reference literature or technical documentation. Keep 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, all electrical circuits have them. Elements of electrical circuits also all without exception possess them.
Harmonized Mode
It is used to ensure maximum transfer of active power, which goes from the power source to the energy consumed. In this case, it is useful to calculate the utility parameter.
When working with this mode, you must be careful and be prepared that part of the circuit will fail (if you do not work out the theoretical aspects in advance).
The main elements during the calculation for electrical circuits
They are used in complex designs to verify what will work and how:
- Branch. This is the name of the section of the circuit on which the same current value. A branch can be composed of one / several elements that are connected in series.
- Node. A place where at least three branches connect. If they are connected to one pair of nodes, then they are called parallel.
- Circuit. Any closed path that goes along several branches is called in a similar way.
These divisions have electrical circuits. Elements of electrical circuits in all cases, except for the branch, are necessarily present in the set.
Conditional positive directions
They must be set in order to correctly formulate equations that describe the processes that occur. The importance of direction is for currents, EMF of power sources , as well as voltages.
Features of drawing markings on the scheme:
- For EMF sources, they are indicated arbitrarily. But it must be borne in mind that the pole toward which the arrow is directed has a higher potential than the second.
- For currents that work with EMF sources, they must coincide with them. In all other cases, the direction is arbitrary.
- For voltages - coincides with current.
Types of electrical circuits
How are they distinguished? If the parameters of the element do not depend on the current that flows in it, then it is called linear. An example is an electric furnace. Non-linear elements of the electric circuit have a resistance that increases with increasing voltage, which is supplied to the lamp.
Laws that will be needed when working with DC circuits
Analysis and calculation will be much more effective if we 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 those values that have currents, voltages, electric-electronic components along the entire electric circuit or in its individual sections. And this is all based on the parameters of the elements that enter them.
Ohm's law for a chain section
For us, the current strength (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 the inverse value: R = I / U.
Ohm's law for the full chain
It determines the relationship that is established between the EMF (E) of a power source for which the internal resistance is r, current and the total equivalent of R. The formula looks like I = E / (r + R). A complex chain usually has several branches. Other power sources may be included. Then using Ohm's law to fully describe the process becomes problematic.
The first law of Kirchhoff
Any node of an electric 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 it are with a minus. The importance of this law is that with its help, a relationship is established between currents that are on different nodes.
Second Law of Kirchhoff
The algebraic sum of the EMF in any selected closed loop is equal to the summed number of voltage drops in all its sections. Is this always the case? Not.
If voltage sources were included in the electric circuit, then this indicator will be zero. When writing an equation according to this law, you must:
- Select the direction in which the loop will be traversed.
- Set positive values for currents, EMF and voltages.
Conclusion
So, we examined electrical circuits, elements of electrical circuits and practical features of interaction with them. Despite the fact that the topic involves an explanation using simple terminology, because of its volume, it is quite difficult to understand. But, having understood it, one can understand the processes occurring in the electric circuit and the purpose of its elements.