Electric circuit and its elements.

Various elements connected by conductors electric current with each other to form electrical circuits. The list of circuit components can be quite long. Exist different types elements of the electric current circuit: passive and active, linear and non-linear, and many others. It is very difficult to enumerate the whole classification.

Types and components

For the circuit to work, it is necessary to have connecting conductors, consumers, and a switch. The circuit must be closed. This is prerequisite operation of the electrical circuit. Otherwise, no current will flow in the circuit. Not all circuits are considered electrical circuits. For example, or grounding is not recognized by them, since in normal mode there is no current in them. However, according to the principle of operation, they are also electrical circuits, since in emergency cases current flows in them. The contour and zeroing is closed with the help of soil.

Internal and external electrical circuits

To create an ordered movement of electrons, you need a potential difference between any part of the circuit. This is ensured by connecting the voltage in the form of a power supply. It is called the internal electrical circuit. The rest of the chain components form the outer chain. To set the movement of charges in the power source against the direction of the field, external forces must be applied.

These forces can be:

• The output of the secondary winding of the transformer.
• Generator winding.

The voltage in the circuit can be both constant and variable, depending on the properties of the power source. On this basis, in electrical engineering, electrical circuits are divided into circuit circuits. Such an explanation of the type of circuit is simplified, since the law of change in the movement of electrons is much more complicated.

In addition to orderly motion, electrons are involved in chaotic thermal motion. The higher the temperature of the material, the greater the speed of the chaotic movement of charge carriers. However, this kind of movement does not participate in the creation of electric current.

The type of current, that is, the properties of the external circuit, also depends on the power source. The battery of cells produces a constant voltage, and the different windings of the generators or give out an alternating voltage. It depends on the internal processes in the power source.

The external forces that create the movement of electrons are called electromotive forces, which are characterized by the work done by the source to move a unit of charge, measured in volts.

In practice, two classes of power sources are used in circuit calculations:

1. Voltage sources.
2. Current sources.

In reality, such ideal springs do not exist, but practically they are trying to imitate. In a household network, we have a voltage of 220 volts with certain normalized deviations. This is a source of tension, since the norm is given precisely for this parameter. The value of the current does not play a big role. At the power plant, a constant voltage value is maintained around the clock, regardless of requests.

The current source works differently. It supports a certain law of electron motion, and the magnitude of the voltage does not matter. An example can be given. For the normal course of welding, it is necessary to maintain constant value current. This function is performed by the inverter electronic unit.

The power supply can be both variable and constant. It doesn't play a big role. It is more important to withstand, for example, the EMF parameter.

Designations of the components of the electrical circuit

This device allows you to connect the consumer to the power source. When using the switch, a spark forms on its contacts. It occurs due to the presence of capacitive resistance. To avoid sparking, chokes are added to the electrical circuit, and contacts are installed in the switch. special kind. Electrical circuits may have other solutions to prevent sparks.

conductors

Most often made from aluminum or copper. This is due to the low resistivity of these metals, although their cost in recent times rises. During operation, heat is generated on the wires, which depends on two parameters:

• Electric current.
• Circuit section resistance.

The electric current is determined by the need of the consumer, therefore, only the resistivity can be changed, which should be as low as possible. All metals reduce resistance as the temperature decreases, resulting in reduced energy losses. If we take , then among them there are samples with a negative and with a positive temperature coefficient of resistance. If we compare the absolute values ​​​​of resistance, then for metals it is much less.

Consumers

All other components of the electrical circuit, except those listed above, are considered consumers. The payload is a simple heating device. Circuit parameters are too dependent on consumers. Electrical circuits have transformer windings that have a large inductive resistance. This negatively affects the transmission of electricity from the source.

In addition to current, direction can also change power. In this case, energy circulates in one direction and in the other. Such power is called reactive, and does not fulfill useful work. However, it heats up the conductors and changes the shape of the electrical signal. Therefore, in industrial environment it is advisable to connect capacitors in parallel to electric motors, which will compensate for the resistance with inductance. As a result, it will close inside the engine, and will not generate excessive heat in the wires.

Inductive consumers have important property: they consume electricity, which turns into a magnetic field and is transmitted further.

In electronics, there are many different consumers that can be divided into classes:

• Active consumers . In order to function, they require electrical energy. From the main network, they practically do not work. These include, microcircuits, and many other types that are peculiar electronic keys. Electric motors differ in that they operate directly from the mains.
• Passive consumers don't need external source nutrition. They pass an electric current through them in a special way. For example, semiconductors (thyristors) begin to pass current only when a certain voltage value is reached. This means that they are passive consumers, and have non-linear current transmission properties. The same types can be classified as passing current in only one direction. In other words, they have the properties of a valve. Also passive consumers are various chokes, capacitors, resistances. In the presence of these components, electrical circuits acquire unusual properties. For example, resonance circuits, consisting of coils and capacitors, are used as filters for different wave frequencies.

Electrical circuit modes

When connecting a different number of consumers to a power source, the power changes, as a result of which there are various modes work in the circuit, and accordingly, the components included in it. In practice, you can imagine the circuit diagram in the form of a passive and active two-terminal network. These are electrical circuits connected to the external part by two terminals with different polarity.

A feature of an active two-terminal network is the presence of an electric current source, a passive two-terminal network does not have it. Equivalent circuits for passive and active elements during operation have become popular. The type of operation mode is determined by the properties of the circuit elements.

Idling

This is the mode when the load is disconnected from the power supply using the key. In this case, the current in the circuit zero. The voltage reaches the EMF level. Circuit elements do not work.

In this case, the switch in the circuit is closed, the resistance is zero, respectively, the voltage is also zero.

When applying the two considered modes, the properties of an active two-terminal network are determined. When the current changes within certain limits, depending on the circuit element, the lower limit is always zero. This element of the circuit begins to supply energy to the circuit. You also need to know that if the voltage is below zero, this means that the active two-terminal resistors consume the energy of the source connected in the circuit, as well as the reserve of the device itself.

Rated mode

This mode is necessary to create technical properties the whole chain and individual components. In this mode, the properties are close to the values ​​specified on the component or in the instructions. It should be noted that each device has its own parameters. However, all devices have three main indicators - these are voltage, power and rated current. All components of electrical circuits also have these indicators.

Negotiated Mode

This mode is used to create the largest transmission transmitted by the power source to the consumer. When working in this mode, care must be taken to avoid failure of part of the circuit.

Main elements of the chain

They are used in complex devices to check the functionality.

• Branch. This is a section of a circuit with a current of the same magnitude. A branch can have several daisy-chained elements.
• Knot. This is the junction of several branches.
• Circuit. This is any closed section of the chain that has several branches.

Electrical circuit – set of devices(elements), intended for the directed movement of electric charges(electric current) and related electromagnetic processes.

Electrical circuit serves to generate, transmit and convert electrical (electromagnetic) energy and signals.

The main elements of an electrical circuit are sources, receivers and transmission lines.

Source of electrical energy and signals – device that converts different kinds energy of non-electromagnetic nature into electromagnetic(galvanic cell, battery, electromechanical generator).

Receiver of electrical energy and electrical signals – a device that converts electrical energy into other forms of energy(electrothermal devices, electric lamps, resistors, electric motors).

Transmission line of electrical energy and electrical signals- conductors (materials, media with free charges) and electromagnetic fields, with the help of which the transmission of electrical energy and signals from sources to receivers is carried out.

In addition, the elements of the electrical circuit can be converting, switching and measuring devices (instruments).

Electrical energy converter – parameter converting device(voltage, current, their shape, magnitude, frequency) electromagnetic energy(transformers, rectifiers, inverters, frequency converter).

Switching devices designed to change the mode of operation of the electrical circuit: turning off and on sources, receivers, changing the parameters of circuit sections. These are contactors, switches, switches, disconnectors.

Measuring devices – devices for measuring various parameters of electromagnetic processes occurring in an electrical circuit(ammeters, voltmeters, wattmeters, etc.).

Electrical circuit diagram – a graphical representation of an electrical circuit containing conditional images of its elements and showing the connection of these elements.

ESKD "Conditional graphic symbols in diagrams". GOST 2.721-74 - 2.758-81.

Receivers, sources:

– galvanic element;

- an incandescent lamp;

– DC generator of electromechanical type;

-resistor;

-potentiometer;

-rheostat;

-inductor;

-capacitor.

Switching devices:

– normally open contact;

– normally closed contact;

- switching contact.

indicating instruments(A, V, W):

Converter devices:

– air transformer;

–diode bridge (full-wave rectifier);

– inverter.

Schematic diagram of the electrical circuit – electrical circuit diagram depicting the connection of real elements of this circuit.

Example. The simplest electrical circuit is a galvanic cell connected to an incandescent lamp through a switch using connecting wires. A voltmeter and an ammeter are included in the circuit to measure voltage and current.

functional(structural, block diagram) – electrical circuit diagram depicting the connection of individual blocks of a complex electrical circuit that perform certain functions(amplification, rectification, inverting, etc.)

bipolar– part of an electrical circuit that is considered with respect to any two clamps.

Quadripole – part of an electrical circuit that has two input and two output terminals.

active circuit – part of an electrical circuit in which sources of electrical energy operate.

passive circuit – part of an electrical circuit in which there is no source of electrical energy.

Circuit equivalent circuit

Neither the functional nor the circuit diagrams of electrical circuits reflect the quantitative side of the electromagnetic processes that take place in the elements of the circuit and which determine the mode of operation of this circuit, regardless of the design and physical nature of these elements.

equivalent circuit(calculated mathematical model, equivalent) electrical circuit–a diagram of an electrical circuit depicting the connections of abstract, ideal elements, with a sufficient approximation of electromagnetic processes in an electrical circuit.

In the theory of electric circuits, the real elements that make up an electric circuit are replaced by abstract ideal elements with certain properties.

What are these elements? And what electromagnetic processes do they reflect?

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Lesson type: a lesson in learning new material and primary consolidation.

Target: to study the components of the electrical circuit, the symbols used in the diagrams.

Tasks:

• educational- provide perception, comprehension and primary consolidation constituent parts electrical circuit, their purpose and symbols.
• Educational- to promote the inculcation of compliance with safety regulations when assembling a chain, interest in physics.
• Educational- to promote the development of the ability to assemble electrical circuits, to depict diagrams of electrical circuits.

Lesson plan.

1. Organizing time(1 min.)
2. Knowledge update. (8 min.)
3. Learning new material. (12 min)
4. Consolidation of knowledge. (15 minutes.)
5. The stage of primary knowledge testing. (5 minutes.)
6. Homework. (1 min.)
7. Summary of the lesson. (1 min.)
8. Reflection. (2 minutes.)

Equipment: galvanic cell, light bulb, key, connecting wires, plates with symbols of EC elements, control table, computer, multimedia projector.

During the classes

1. Org. Moment (explain group work)

Electricity all around
The plant and the house are full of them.
Life is drastically made easier!
It's amazing,
For our benefit,
All wires Majesty
It's called electricity!

2. Actualization of knowledge.

Each group is invited to choose a sheet with the question:

• What is electric current?
• What conditions are necessary for the existence of an electric current?
• Why is electricity needed?
• Direction of electric current?

(To prepare students for the GIA, it is necessary to include in various stages lesson and homework, a variety of tasks that will contribute to the formation of methodological knowledge and skills - a task with a choice of answers, the level of experimental skills, the ability to solve a qualitative problem, as well as tasks for working with a text of physical content.)

When repeating the material, students are offered the following task: (slide 2)

3 . Using the letters in the lines, enter the names of the current sources:

slide 3

4. Learning new material.

Lesson topic: « Electrical circuit».

Open your notebooks and write down the topic of the lesson. The set of devices through which electric current flows is called electrical circuit. Chains are simple (as in a demonstration) and complex (wiring), but in all it is possible to distinguish components. Devices that use electrical energy are called consumers. This is the first part of the chain. Give examples of consumers… in the classroom… at home… on the table… (for L. R. light bulb). The second component of the circuit is a current source (for L.R. - a galvanic cell). The current source is connected to the circuit last with the help of connecting wires - this is the third component of the circuit. There is one more main part electrical circuit. In Paris in 1881, at an electrical exhibition, everyone was delighted with this invention. This is a switch. Its role is to close and open the electrical circuit. In technology, different types of closing and opening devices are used. In order for there to be current in the circuit, it must be closed, i.e. consist of conductors of electricity. If at any point the wire breaks, then the current in the circuit will stop. This is what switches work on. Name the locking devices in the class (Switch, knife switch, buttons, for l.r. - key) slide 4.

Please note: the circuit is assembled with the switch open; the switch is made of conductors of electricity, and you need to touch the insulating handle.

So, what are the components of an electrical circuit? Write in your notebook:

• consumer
• current source
• connecting wires
• closing device

You have a page of G.N. Stepanova, the peculiarity of the textbook is that in each paragraph there is a keyword, in the first one, for example, “Electric circuit”, we will place it in the center. In the rest, the components of the chain blocks. In the margins, what is included in the blocks and as indicated on the diagram. On the table for each group is a netbook, on the desktop is a file with the word cluster. We open it and make a cluster using the tutorial.

Electrical circuits can be complex. The TV is out of order, and you need information about what the electrical circuit consists of, and the information is contained in the electrical circuits. Electrical circuits- these are drawings that show how to connect the elements of an electrical circuit.

Guys, you have to do practical work.

What safety rules will you follow?

Practical work.

Target: assemble an electrical circuit from the devices that everyone has on the tables so that the light bulb lights up.

A simple circuit is assembled in groups (power source, lamp, key, connecting wires)

Completing of the work. Drawing up a diagram. The teacher checks.

5. Stage of primary testing of knowledge.

Individual tasks: arrange the cond. designations by "places", connecting with an arrow conditional. symbol with the name of the device.

Let's check using control table: