Electrical circuit: elements, principle of operation. Electrical circuit and its elements

In this lesson, we will repeat the conditions for the existence electric current and consider such a concept as an electrical circuit and its main elements. At the end of the lesson, we will specific example assembling the electrical circuit of a flashlight.

Topic: Electromagnetic phenomena

Lesson: Electric circuit and its components

Recall that in the last lesson we specified three conditions for the presence of an electric current:

1. the presence of charges;

2. the presence of a current source (galvanic cell, etc.). The current source creates electric field inside the conductor, which is the cause of the movement of charges;

3. the presence of an electrical circuit. We will talk about the latter concept today.

The electrical circuit must contain a current source (Fig. 1-3), i.e. an element that creates an electric field in the circuit and ensures the movement of charged particles, and a current consumer, i.e., for example, any household appliance(Fig. 4): light bulb, flashlight, computer, TV, washing machine, refrigerator, etc. The current source and consumers are always connected by wires (conductors), i.e., such elements that are capable of conducting electric current and have large quantity free charged particles.

Rice. 1. Galvanic cell ()

Rice. 2. Accumulator ()

Rice. 3. Power plant ()

Thus, the electrical circuit has the following main components: current source, current consumers, connecting wires.

Of course, current consumers themselves consist of smaller elements, each of which has its own name, function and features. Electrical circuits are complex and simple, we will begin their study with the simplest options, for example, with a flashlight device. Its components include: a power source, a light bulb, connecting wires and a switch. At the end of the lesson, we will assemble an electrical circuit similar to the circuit inside a flashlight and discuss how it works.

For convenience, electrical circuits are usually depicted in the form of diagrams in which certain notations are accepted. various elements. The symbols for the elements of electrical circuits are known and classified in a certain way, there are a lot of them, but we will get acquainted with the main ones.

Definition. Electrical circuit shown in the figure is called electric circuit.

The elements indicated in the table are components of the simplest electrical circuits.

Consider the simplest electrical circuit using the example of a flashlight device. It includes a power source, an incandescent bulb, connecting wires and a switch (key).

It is convenient to assemble the circuit in the following sequence: first, connect the light bulb to one of the poles of the current source (battery), then connect the second contact on the light bulb to the previously opened key (switch) and, to close the circuit, connect the second contact of the key to the free pole of the current source.

After assembling the circuit, it can be seen that the bulb is not lit, because it is still open with the key, and the electric current does not flow (the condition for the electrical circuit to be closed is not met). Now we close the key, and the light bulb lights up (Fig. 5), because the circuit becomes closed and all the conditions for the existence of an electric current are met.

Rice. 5.

Let's draw a diagram of the electrical circuit we have assembled using the symbols given in the table (Fig. 6).

Rice. 6.

Of course, it is pointless to consider from a practical point of view those electrical circuits in which the work of an electric current is not performed. We will talk about the action of electric current and the performance of work by it later.

In the next lesson, our topic will be "Electric current in metals."

Bibliography

1. Gendenshtein L.E., Kaidalov A.B., Kozhevnikov V.B. Physics 8 / Ed. Orlova V.A., Roizena I.I. - M.: Mnemosyne.
2. Peryshkin A. V. Physics 8. - M .: Bustard, 2010.
3. Fadeeva A. A., Zasov A. V., Kiselev D. F. Physics 8. - M .: Education.

Additional precommended links to Internet resources

1. Academician ().
2. Internet portal Mukhin.ru ().
3. youtube().

Homework

1. Page 78: questions No. 1-4, p. 79: exercise No. 13. Peryshkin A.V. Physics 8. - M .: Bustard, 2010.
2. At your disposal there is a galvanic cell, a light bulb, two keys and connecting wires. draw circuit diagram an electrical circuit in which the bulb lights up only when both keys are turned on.
3. Iron nail and cut copper wire stuck in a lemon. Will current flow through the wire that connects the nail and the copper wire?
4. Three wires hang from the ceiling at the place where the chandelier is attached, through which current flows after the chandelier is connected. If the chandelier is connected correctly, the two switches work in such a way that one of them turns one lamp on and off, and the other - the other three. Draw a connection diagram for lamps in a chandelier, switches and a power source.

This article is for those who are just starting to study the theory of electrical circuits. As always, we will not go into the jungle of formulas, but we will try to explain the basic concepts and the essence of things that are important for understanding. So, welcome to the world of electrical circuits!

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Electrical circuits

is a set of devices through which electric current flows.

Consider the simplest electrical circuit. What does it consist of? It has a generator - a current source, a receiver (for example, a light bulb or an electric motor), as well as a transmission system (wires). In order for a circuit to become a circuit, and not a set of wires and batteries, its elements must be interconnected by conductors. Current can only flow in a closed circuit. Let's give another definition:

- These are interconnected current source, transmission lines and receiver.

Of course, source, sink and wires is the simplest option for an elementary electrical circuit. In reality, different chains include many more elements and auxiliary equipment: resistors, capacitors, knife switches, ammeters, voltmeters, switches, contact connections, transformers and more.

Classification of electrical circuits

By appointment, electrical circuits are:

• Power electrical circuits;
• Electrical control circuits;
• Electrical measurement circuits;

Power circuits intended for transmission and distribution electrical energy. It is the power circuits that conduct current to the consumer.

Also, the circuits are divided according to the strength of the current in them. For example, if the current in the circuit exceeds 5 amperes, then the circuit is power. When you click on the kettle plugged into the outlet, you close the power circuit.

Electrical control circuits are not power and are designed to actuate or change operating parameters electrical devices and equipment. An example of a control circuit is monitoring, control and signaling equipment.

Electrical measurement circuits designed to record changes in the parameters of electrical equipment.

Calculation of electrical circuits

To calculate a circuit means to find all the currents in it. Exist different methods calculation of electrical circuits: Kirchhoff's laws, the method of loop currents, the method of nodal potentials and others. Consider the application of the method of loop currents on the example of a specific circuit.

First, we select the circuits and denote the current in them. The direction of the current can be chosen arbitrarily. In our case, clockwise. Then for each contour we will compose equations according to the 2nd Kirchhoff law. The equations are compiled as follows: The loop current is multiplied by the loop resistance, the products of the current of other loops and the total resistances of these loops are added to the resulting expression. For our schema:

The resulting system is solved by substituting the initial data of the problem. The currents in the branches of the original circuit are found as the algebraic sum of the loop currents

In an electrical circuit, there must be a source of movement of electrically charged particles, which is called electric current. In other words, the electric current must have its own exciter. Such a current exciter, called a source (generator), is an integral element of an electrical circuit.

Electric current can cause various effects in nature - for example, it makes incandescent bulbs glow, it drives heating devices and electric motors. All these devices and devices are commonly called receivers of electric current. Since current flows through them, that is, they are included in the electrical circuit, the receivers are also elements of the circuit.

The flow of current requires that there be a connection between the source and the receiver, which is implemented using electrical wires, representing the third important constituent element electrical circuit.

Electrical circuit- a set of devices designed for the passage of electric current. The circuit is formed by energy sources (generators), energy consumers (loads), energy transmission systems (wires).

An electrical circuit is a set of devices and objects that form a path for electromagnetic processes in which can be described using the concept of electromotive force, current and voltage.

The simplest electrical installation consists of a source (galvanic cell, battery, generator, etc.), consumers or (incandescent lamps, electric heaters, electric motors, etc.) and connecting wires connecting the clamps of the voltage source to the clamps of the consumer. Those. electrical circuit - a set of interconnected sources of electrical energy, receivers and wires connecting them (transmission line).

Fig.1. Electrical circuit diagram

The electrical circuit is divided into internal and external parts. The source of electrical energy belongs to the internal part of the electrical circuit. The external part of the circuit includes connecting wires, consumers, switches, switches, electrical measuring instruments, i.e., everything that is connected to the terminals of the source of electrical energy.

Electric current can only flow through a closed electrical circuit. An open circuit anywhere causes the electrical current to stop.

Circuit power sources are galvanic cells, electric accumulators, electromechanical generators, thermal electrical generators, photocells, etc. modern technology Electric generators are mainly used as energy sources. All power sources have a value which is small compared to the resistance of other elements of the electrical circuit.

DC electrical receivers are electric motors that convert electrical energy into mechanical, heating and lighting, electrolysis plants, etc.

As auxiliary equipment, an electrical circuit includes devices for switching on and off (for example, knife switches), devices for measuring electrical quantities (for example, ammeters and voltmeters), protection devices (for example, fuses).

All electrical receivers are characterized by electrical parameters, among which the main ones are voltage and power. For normal operation the electrical receiver on its terminals must be supported.

Elements of the electrical circuit are divided into active and passive. To active elements of the electrical circuit include those in which EMF is induced (EMF sources, electric motors, batteries during charging, etc.). To passive elements include electrical receivers and connecting wires.

For a conditional representation of electrical circuits, electrical circuits are used. In these diagrams, sources, receivers, wires and all other devices and elements of the electrical circuit are indicated using conventional symbols (graphic symbols) made in a certain way.

According to GOST 18311-80:

Power circuit- an electrical circuit containing elements whose functional purpose is to produce or transmit the main part of electrical energy, its distribution, conversion into another type of energy or into electrical energy with other parameter values.

Auxiliary circuit of an electrical product (device)- an electrical circuit of various functional purposes, which is not a power electrical circuit of an electrical product (device).

Electrical control circuit- an auxiliary circuit of an electrical product (device), the functional purpose of which is to actuate electrical equipment and (or) individual electrical products or devices or to change the values ​​of their parameters.

Alarm circuit- an auxiliary circuit of an electrical product (device), the functional purpose of which is to actuate signaling devices.

Measurement circuit- an auxiliary circuit of an electrical product (device), the functional purpose of which is to measure and (or) register parameter values ​​and (or) obtain measurement information of an electrical product (device) or electrical equipment.

According to topological features electrical circuits are divided into:

into simple (single-circuit), two-node and complex (multi-circuit, multi-node, planar (planar) and volumetric);

bipolar, having two external outputs (two-terminal networks and multi-pole, containing more than two external outputs (quadruple, multi-terminal).

Sources and receivers (consumers) of energy from the point of view of circuit theory are two-terminal, since for their operation it is necessary and sufficient to have two poles through which they transmit or receive energy. This or that two-terminal network is called active if it contains a source, or passive - if it does not contain a source (respectively, the left and right parts of the circuit).

Devices that transmit power from sources to sinks are four terminals, as they must have at least four terminals to transfer power from the generator to the load. Wires are the simplest device for transmitting energy.

Elements of an electrical circuit that have electrical resistance and are called resistors are characterized by the so-called volt-ampere characteristic - the dependence of the voltage at the terminals of the element on the current in it or the dependence of the current in the element on the voltage at its terminals.

If the resistance of an element is constant at any value of the current in it and any value of the voltage applied to it, then the current-voltage characteristic is a straight line and such an element is called line element.

In general resistance depends on both current and voltage. One of the reasons for this is the change in the resistance of the conductor when current flows through it due to its heating. As the temperature rises, the resistance of the conductor increases. But since in many cases this dependence is insignificant, the element is considered linear.

An electrical circuit, the electrical resistance of the sections of which does not depend on the values ​​\u200b\u200band and the voltages in the circuit, is called linear electrical circuit. Such a chain consists only of linear elements, and its state is described by linear algebraic equations.

If the resistance of a circuit element depends significantly on current or voltage, then the current-voltage characteristic is non-linear, and such an element is called non-linear element.

An electrical circuit, the electrical resistance of at least one of the sections of which depends on the values ​​\u200b\u200band on the directions of currents and voltages in this section of the circuit, is called. Such a circuit contains at least one non-linear element.

When describing the properties of electrical circuits, a connection is established between the magnitudes of the electromotive force (EMF), voltages and currents in the circuit with the values ​​of resistances, inductances, capacitances and the method of constructing the circuit.

When analyzing electrical circuits use the following topological parameters of circuits:

• branch - a section of an electrical circuit along which the same electric current flows;
• node - the junction of the branches of an electrical circuit. Usually, the place where two branches are connected is not called a node, but a connection (or a disposable node), and a node connects at least three branches;
• circuit - a sequence of branches of an electrical circuit that forms a closed path, in which one of the nodes is both the beginning and end of the path, and the rest meet only once.

Technological map of the lesson

Dudareva E.M. physics teacher MBOU gymnasium №11

Academic subject: physics

Grade: 8

UMC: Peryshkin A.V.

Lesson topic: Electrical circuit and its components

Lesson type: learning new material.

The purpose of the lesson: reveal the essence constituent parts electrical circuit, their purpose and symbols.

Lesson objectives:

a) the formation of ideas about the electrical circuit, the organization of the assimilation of basic concepts on this topic, the formation of the scientific worldview of students (subjective result).

b) development of the ability to generate ideas, identify cause-and-effect relationships, work in a group, use alternative sources information, to form the ability to analyze facts when observing and explaining phenomena, when working with the text of the textbook (metasubject result).

in) developing skills to manage learning activities, the formation of interest in physics in the analysis of physical phenomena, the formation of motivation by setting cognitive tasks, revealing the connection between theory and experience, developing attention, memory, logical and creative thinking(personal result).

Teaching methods: reproductive, problem, heuristic.

Forms of organization cognitive activity students: collective, individual, group.

Means of education: textbook, laboratory equipment, reflection cards, rating table, multi-level didactic material, computer, projector, Internet.

During the classes

Teacher activity

Student activities

Cognitive

Communicative

Regulatory

Formed ways of doing things

Implemented learning activities

Formed ways of doing things

Implemented learning activities

Formed ways of doing things

1. Organizing time.

"Hello. I'm glad to see you today! Look at each other, smile, send positive emotions to their classmates."

“Choose the “muzzle” that matches your mood in this moment time"

Greeting students, analysis of selected faces

Respond to the teacher's greeting.

Interact with the teacher

Listening to the teacher

goal setting

Ability to prepare for work

2. Setting the goal and objectives of the lesson

“Today, during the lesson, you will enter the scores into the rating tables, and at the end of the lesson, transfer the scores to the assessment.”

Talks about what in Due to the widespread use of electricity, there is a need for a more thorough study of the electric current. Take a power source and a light bulb. What needs to be done to make it ignite?

Clarification of the topic of the lesson and the formulation of its purpose. Problem statement

Answer the teacher's questions. Make assumptions about the topic of the lesson "Electric circuit and its components."

Extraction of essential information from the words of the teacher. Realization of actualization of personal life experience.

Interact with the teacher

Listening to the teacher and comrades, building clear statements for the interlocutor.

Checking the correctness of students' answers

Ability to listen in accordance with the target setting. Acceptance and preservation of the educational goal and task. Clarification and addition of students' statements

3. Updating knowledge

“Before we get acquainted with the topic of the lesson, it is necessary to recall the previous material. AT perform the following task: using the letters in the lines, enter the names of the current sources ":

Interview with students on:

What is electric current?

What needs to be created in a conductor in order for an electric current to arise in it?

Where is the electric field created?

What happens in the current source?

Where are the separated particles located?

Will there be an electric current in a rubber cord connected to a current source? And in the coil of wire that lies on the table?

What is the purpose of generating electricity?

What current sources do you know?

What energy transformations take place inside the current source?

Gives assignments to students. Monitors independence in completing tasks.

Perform tasks on their own.

Answers:

thermoelement, photocell, accumulator, generator.

They exchange work with a neighbor on the desk, check the work of a neighbor, give points. (For the correct word - 1 point)

Answer the teacher's questions.

The competence of students in the field of physics.

Interact with the teacher

Listening to the teacher

Mutual control of the task in pairs.

Self control.

4. Primary assimilation of new knowledge

The set of devices through which electric current flows is called an 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. Used in technology different types closing and opening devices. 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)

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?

Consumer

Current source

Connecting wires

Closing device Electrical circuits can be complex. The TV is out of order, and you need information about what the electrical circuit consists of. Therefore, they came up with the elements of the chain to depict using symbols. To avoid confusion, use standard set characters.

Working with the textbook (Figure 48), the teacher attaches the tablets with symbols to the board, the students write them down in a notebook.

Demonstration assembling a circuit (with the involvement of students), consisting of a current source, a light bulb, a key and connecting wires. Why isn't the light on? Let's close the chain. An electrical circuit is a closed path along which charge flows from one pole of a current source to the other.

Let's draw a diagram of this circuit. (1 student goes to the blackboard) The scheme must be neat and accurate. Let's check according to figure 49 of the textbook.

Demonstration of EOR "Assembly of an electric circuit". ( )

Explains new material, asks questions to students, demonstrates the assembly of the chain.

Gives the task to work with the drawing of the textbook, write down the symbols in a notebook. EOR demonstration.

Listen to teachers and answer questions.

Observation of the physical experiment of the teacher, of the ESM material. They work with the textbook material, highlight essential information, draw symbols and a diagram in a notebook.

Formation of research activities, research culture, the ability to observe, draw conclusions.

They unite efforts to solve the problems posed, perform the task independently. Discuss the experiment.

Aligning efforts to resolve learning task to agree and come to a common opinion in joint activities, to take into account the opinions of others

Self-control and mutual control.

Ability to listen in accordance with the target setting. Plan your actions. Correct your actions. Acceptance and preservation of the educational goal and task. Clarification and addition of students' statements.

5. Initial check of understanding

“Guys, soon you will have to think about the choice future profession, and now imagine that you are electricians and you have EC circuits in front of you. Name what devices they consist of, and find a "defect" in each of the circuits.

Do practical work.

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

Make a diagram.

The task is given according to the textbook: (exercise 13 No. 2) draw a circuit diagram containing one galvanic cell and two bells, each of which can be turned on separately.

Gives students tasks to complete in pairs a task on cards, a physical experiment.

Give students the task to work with the textbook. Listens and checks for correct execution.

Find a "defect" in the circuits, perform practical task. Complete the task in the textbook.

Highlighting essential information. Logical inferences.

Participate in frontal discussions.

Listen to students' answers and be able to formulate own opinion and position, be able to use speech to regulate their actions.

Checking the correctness of students' answers.

Self-control of understanding of tasks.

Listening skills. Acceptance and preservation of the educational goal and task. Clarification and addition of students' statements.

Implementation of self-control and mutual control.

6. Primary fastening

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

2 people receive differentiated task: issued homemade switch, made according to page 180 of the "Big Book of Experiments". M. Rosmen 2001. It is a device: 2 buttons are fixed on a wooden board, which can be connected to each other with a metal clip. Ask students to rate technical properties this switch.

Formulation of task conditions.

The performance of a differentiated task is discussed. This switch is quite simple, it can be easily made at home, but it has small flaw, since it consists of an uninsulated conductor. To use it, you need to move it with a dielectric, for example, a plastic stick, so that it does not shock.

Perform tasks. Perform cross-checking. Put points in the rating table. They listen to their comrades performing a task of a heuristic nature.

Reinforce knowledge gained in class.

Consciously and voluntarily build a speech statement in oral form.

Participate in face-to-face discussion of answers to questions

Understand the answers of students by ear, be able to formulate their own opinion and position, be able to use speech to regulate their actions

Checking the correctness of students' answers.

Self-control of understanding questions and knowing the correct answers.

Ability to listen in accordance with the target setting. Acceptance and preservation of the educational goal and task. Clarification and addition of students' statements.

The exercise of self-control.

7. Homework

Required level: § 33, exercise 13 (No. 5); elevated level: exercise 13 (No. 3); creative task: assemble the simplest circuit on a battery and arrange it in the form of a toy.

Formulation of homework, instructions for its implementation

Listen to the teacher and write down the homework in the diary.

Extraction of essential information from the words of the teacher.

Interact with the teacher

Listening to the teacher

Development of regulation of educational activity.

Regulation of educational activity.

8. Summary of the lesson

« R guys, remember the purpose of our lesson.

What are the components of an email? chain?"

Students are graded.

Formulates a question

They answer the question: “What are the components of email. chain".

Consciously and voluntarily build a speech statement in oral form. Choose the face that suits your mood at the moment.

Conducts reflection and analysis.

Reflect.

The ability to draw conclusions.

Interact with the teacher

Be able to formulate your own opinion

Self-regulation of emotional and functional states.

Self-regulation

Physics lesson Grade 8

Topic: "Electric circuit and its components"

Objectives: to study the components of the electrical circuit, the symbols used in the diagrams, to carry out measuring and calculation actions

Didactic - create conditions for consolidation educational material using research technologies and physical experiment;

Educational: to continue the formation of skills and abilities to assemble the simplest electrical circuits, as well as use measuring instruments(ammeter and voltmeter), carry out simple mathematical calculations

Educational: continue to educate the attitude towards physics as an experimental science; to continue work on the formation of skills to work in a team; fix the safety rules when assembling the chain,

Developing: to continue work on the formation of skills to draw conclusions and generalizations; continue the development of thinking, creative and research abilities of students. Develop cognitive interest in the subject.

Equipment: computer, projector, current sources, electric bell, wires, key, bulb, ammeter, voltmeter, test material, table,

During the classes.

1. Organizational moment.

2 Updating knowledge.

Checking homework: testing (2 options for 5 questions).

3. Learning new material.

Motivation Q: What is needed for an incandescent lamp to produce light?

Imagine, for a moment electric lamps go out in the houses, TVs turn off, the movement of electric trains, trolleybuses stops, then they say that the current has disappeared in the wires.

What is current?

An electric current is an ordered (directed) movement of charged particles.

Conditions for the occurrence of electric current:

The presence of a conductor;

The presence of an electric field created by a current source, in which, due to energy of non-electric origin, work is done to separate charged particles;

The presence of a closed circuit.

Current sources are used to conduct current to consumers (lamps, tiles, irons, televisions, computers, and other electrical appliances). In order to use the energy of an electric current, you need to have current source .

Televisions, computers, incandescent lamps (energy saving), household appliances are called receivers or electrical energy consumers .

Electrical energy must be delivered to the consumer. To do this, the receiver is connected to a source of electrical energy. wires .

To turn on and off in right time consumers of electrical energy keys, switches, buttons, switches , that is, closing and opening devices.

Demonstration: demonstrate to students from laboratory equipment a current source, keys, consumers, wires.

For there to be current in a circuit, it must be closed. If there is a break in any place, then the current in the circuit will stop. This is the basis for the operation of the switches.

Devices on the diagrams indicate conventional signs.

We fill in the table together with the students (2 columns).

The simplest electrical circuit consists of a current source, an electricity consumer, a closing and opening device, and connecting wires.

4. Primary check of understanding of the studied

1. The main elements of the electrical circuit? (power source, power consumer, wires, closing and opening devices)

2. How many current sources have poles? (two: positive and negative)

3. What current sources and consumers do you know? (sources: battery, generator, galvanic cell; consumers: electrical appliances, lamps).

5. Consolidation of the studied (problem solving).

6. Reflection: name the consumers of electrical energy that are used at home?

7. Homework: § 33 Ex. 13 No. 2, 3, 5.

Literature:

Peryshkin A.V. Physics 8th grade - Moscow: Bustard, 2009.

Lukashik V.I., Ivanova E.V. Collection of problems in physics 7-9.- Moscow: Education, 2008.

Chebotareva A.V. Physics tests Grade 8. - Moscow: Exam, 2010.

Peryshkin A.V. Collection of problems in physics 7-9.- Moscow: Exam, 2010.

Sources of illustrations, Internet resources: http://class-fizika.narod.ru/

Memo on safety when working with electric current.

Do not use wires with damaged insulation with visible damage when assembling electrical circuits.

Check that all fixtures and fittings are in good working order.

When assembling electrical circuits, avoid crossing wires.

Connect power sources last.

All corrections in the circuits are carried out with the current source turned off.

Do not touch rotating parts of electrical machines.

Do not determine the presence of current in the circuit by touch.

Do not touch wires hanging from poles, walls sticking out of the ground - they may be energized.

Chain assembly tasks:

a) Assemble a chain consisting of a source, a bell, a key. Draw a diagram.

b) Assemble a circuit consisting of a source, an electric motor, a key. Draw a diagram.

c) Assemble a circuit consisting of a source, two lamps, a key, so that the key turns on both lamps. Draw a diagram.

d) Assemble a circuit consisting of a source, two lamps, two keys, so that the keys turn on the lamps separately. Draw a diagram.

e) Assemble a circuit consisting of a source, two lamps, two keys, so that the keys turn on the lamps separately. Draw a diagram.

f) Assemble a circuit consisting of a source, a lamp, a bell, a key, so that the key turns on the bell and the lamp together. Draw a diagram.

g) Assemble a circuit consisting of a source, two electric motors, two keys, so that the keys turn on the motors separately. Draw a diagram.