Obzh message on the subject of electricity. Abstract of a lesson on life safety in the preparatory group for school “Magic electricity. crossword entry - what happened - word - dangerous
Electricity is the orderly movement of electric charges. The current strength in the circuit section is directly proportional to the potential difference (i.e., the voltage at the ends of the section) and inversely proportional to the resistance of the circuit section.
The nature and depth of the impact of electric current on the human body depend on the strength and type of current, the time of its action, the path of passage through the human body, the physical and mental state of the latter.
The threshold (sensible) current is about 1 mA. At a higher current, a person begins to feel unpleasant painful muscle contractions, and at a current of 12–15 mA, he is no longer able to control his muscular system and cannot independently break away from the current source. Such a current is called non-letting. The action of a current of more than 25 mA on muscle tissue leads to paralysis of the respiratory muscles and respiratory arrest. With a further increase in current, fibrillation (convulsive contraction) of the heart may occur. A current of 100 mA is considered lethal.
Alternating current is more dangerous than direct current. It matters what parts of the body a person touches the current-carrying part. The most dangerous are those ways in which the brain or spinal cord (head and arms, head - legs), heart and lungs (arms - legs) are affected.
A characteristic case of getting under voltage is contact with one pole or phase of a current source. The voltage acting on a person in this case is called the touch voltage. Particularly dangerous are the areas located on the temples, back, backs of the hands, shins, back of the head and neck.
The effect of electric current on the body is characterized by the main damaging factors:
1) an electric shock that excites the muscles of the body, leading to convulsions, respiratory and cardiac arrest;
2) electrical burns resulting from the release of heat during the passage of current through the human body. Depending on parameters electrical circuit and human condition may experience skin redness, burn formation;
3) blisters or charring of tissues; when the metal is melted, metallization of the skin occurs with the penetration of pieces of metal into it.
The effect of current on the body is reduced to:
1) heating;
2) electrolysis;
3) mechanical impact.
The mechanical action leads to tissue rupture, delamination, shock effect of the evaporation of fluid from the tissues of the body.
During thermal action, overheating and functional disorder of organs in the path of current flow occur.
The electrolytic effect of the current is expressed in the electrolysis of fluid in the tissues of the body, a change in the composition of the blood.
If there are tissue changes at the site of exposure to electric current, a dry aseptic bandage is applied to the affected part of the body.
To avoid electric shock, it is necessary to carry out all work with electrical equipment and devices after disconnecting them from the electrical circuit.
ESD protectionConstant electrostatic field (ESF) is a field of fixed charges that interacts between them.
The occurrence of static electricity charges occurs during deformation, crushing (spraying) of substances, relative movement of two bodies in contact, layers of liquid and bulk materials, with intensive mixing, crystallization, and also due to induction.
When dielectrics are rubbed, excess charges appear on their surface, electric charges accumulate on dry hands, creating a potential of up to 500 V. The potential difference between a thundercloud and the Earth reaches huge values, measured in hundreds of millions of volts, and a strong electric field arises in the air.
Under favorable conditions, breakdown occurs. Charges tend to accumulate to a greater extent on points or bodies similar in shape to points.
Near these sharp points, high electric fields. For this reason, lightning strikes high free-standing objects (towers, trees, etc.), and therefore it is dangerous for a person to be in open space during a thunderstorm or near individual trees, metal objects.
Along with natural static electric fields in the technosphere and in everyday life, a person is exposed to artificial static electric fields.
Artificial static electric fields are due to the increasing use for the manufacture of household items:
1) toys;
3) clothes;
4) for interior decoration of residential and public buildings;
5) for the manufacture of building parts of production equipment;
6) equipment;
7) tools;
8) machine parts of various synthetic polymeric materials;
9) dielectrics.
Permissible levels of electrostatic fields are set in GOST 12.1.045-84.
The use of protective equipment for workers is mandatory in cases where the actual levels of electrostatic fields in the workplace exceed 60 kV / m 2.
When choosing means of protection against static electricity, the features of technological processes, physical and chemical properties of the material being processed, the microclimate of the premises and others, which determine a differentiated approach in the development of protective measures.
Common means of protection against static electricity are to reduce the generation of electrostatic charges or their removal from the electrified material, which is achieved by:
1) grounding of metal and electrically conductive elements of equipment;
2) an increase in the surface and volume conductivity of dielectrics;
3) installation of neutralizers of static electricity.
Grounding is carried out regardless of the use of other protection methods.
The electrical saturation of modern geological exploration production (electrical installations, devices, units) forms electrical hazard. When working with electrical installations in production, household appliances, electrical safety requirements must be observed. They are a system of organizational and technical measures and means that protect people from the harmful and dangerous effects of electric current.
In the course of geological exploration, in most cases, a 380/220 V electrical network with a solidly grounded neutral is used. The electrical network diagram is shown in fig. 5.2.
Rice. 5.2. Scheme of an electrical four-wire network with a solidly grounded neutral
The voltage between any two phases is called linear voltage, which is equal to 380 V. The voltage between any phase and the neutral wire is called phase and is equal to 220 V. According to the PUE, the neutral wire of the network is connected to the ground loop at least at two points.
The effect of electric current on the human body. The effect of electric current on the human body is diverse. Passing through the human body, the electric current causes thermal, electrolytic and biological effects.
The thermal effect of the current is manifested in burns of the body, heating to a high temperature of the internal organs of a person ( blood vessels, heart, brain).
The electrolytic effect of the current is manifested in the decomposition of organic body fluids (water, blood) and violations of their physical and chemical composition.
The biological effect of the current is manifested as irritation and excitation of the living tissues of the body and is accompanied by involuntary convulsive contractions of the muscles (heart, lungs).
These actions result in two types of injury: electrical injury and electrical shock.
Electrical injuries are clearly defined local damage to the tissues of the human body caused by exposure to electric current (or arc). Electrical injuries are curable, although the severity can be significant up to the death of a person. There are the following electrical injuries:
- 1) electrical burns;
- 2) electrical signs;
- 3) metallization of the skin;
- 4) electrophthalmia;
- 5) mechanical damage.
An electrical burn occurs with significant voltages and imperfect contact of a person with current-carrying parts.
With perfect contact, electrical signs appear - clearly defined spots of gray or pale yellow color on the surface of human skin.
Metallization of the skin is the penetration into the upper layers of the skin of the smallest particles of metal, graphite. Soreness is caused by the heating of these particles.
Electrophthalmia - eye damage caused by intense radiation of an electric arc (harmful ultraviolet and infrared rays).
Mechanical damage occurs as a result of sharp involuntary convulsive contractions of the muscles, up to ruptures of the skin, blood vessels, dislocations of the joints and bone fractures. Possible secondary consequences caused by a fall from a height, involuntary impacts.
Electric shock is the result of the biological action of current. The excitation of the internal living tissues of the body by an electric current passing through it is accompanied by involuntary convulsive muscle contractions. If the latter belong to the respiratory organs or especially the heart, severe consequences (clinical, biological death) are possible due to the cessation of the work of breathing, heartbeat and the onset of electric shock. With clinical death, a person has no signs of life (no breathing and heartbeat), but life in the body has not died out and is maintained at a low level for 6-8 minutes. If you do not start reviving the body, then the death of those very sensitive to oxygen starvation cortical cells (neurons). With the expiration of the specified time, biological death may occur.
Factors that determine the risk of electric shock. The nature and consequences of human exposure to electric current depend on the following factors:
- electrical resistance of the human body (Rch);
- voltage (E) and current (J);
- duration of exposure to electric current (t);
- current paths through the human body;
- type and frequency of electric current;
- environmental conditions;
- individual properties of a person.
Electrical resistance to current is provided mainly by the skin, and in its composition - the outer stratum corneum (epidermis). In a dry state, human skin is a dielectric with a volume resistivity of up to 105 ohm. The resistance of internal (wet) tissues is thousands of times less, about 300-500 ohms. As a calculated value for alternating current of industrial frequency, the active resistance of the human body is equal to 1000 ohms. Damage to the stratum corneum (cuts, scratches, abrasions) reduces the resistance of the body to 500-700 ohms, which proportionally increases the risk of electric shock to a person. Moisturizing or contamination of the skin at elevated temperatures, which causes increased sweating, has the same negative value. The skin of the face, neck, armpits has the least resistance, and vice versa, the skin of the palms and soles have increased resistance. With an increase in the time of action of voltage, current strength and frequency, the resistance of the skin drops sharply, which aggravates the consequences of the passage of current through the human body.
The magnitude of the current and voltage. The main factor determining the outcome of an electric shock is the strength of the current passing through the human body. Current strength - the amount of electricity passing through the human body per unit time. The greater the current, the more dangerous its effect. There are three stages of the impact of current on the human body and the corresponding three threshold values: perceptible, non-release and fibrillation.
A perceptible current causes perceptible painless irritations. A person can independently free himself from a wire or live part that is energized. If a person is exposed to an alternating current of industrial frequency (f = 50 Hz), he begins to feel the current flowing through him when its value reaches 0.6-1.5 mA. For direct current, this threshold value is 6-7 mA.
The non-release current causes an irresistible convulsive contraction of the muscles of the hand in which the conductor is clamped. In this case, the strength of the alternating current flowing through the body should be 10-15 mA or more, and the direct current should be 50-70 mA. A person cannot independently open his hand and free himself from the effects of current.
Fibrillation current causes fibrillation (flutter) of the heart muscle. These are fast chaotic and non-temporal contractions of the fibers of the heart muscle (fibrils). As a result, the heart loses its ability to pump blood, the processes of blood circulation and respiration stop in the body, and death occurs. When exposed to alternating current of industrial frequency, the value of the threshold fibrillation current is 100 mA (with a duration of 0.5 sec), and for direct current - 300 mA for the same duration. A current greater than 5 A does not cause cardiac fibrillation, instant cardiac arrest occurs.
Duration of exposure to electric current. The duration of the passage of current through the human body has a significant impact on the outcome of the lesion. Prolonged action of the current leads to severe and sometimes fatal injuries. With an increase in the passage time of the current, the resistance of the human body decreases, as this increases the local heating of the skin, which leads to the expansion of its vessels, to an increase in the supply of blood to this area and an increase in sweating.
The path of electric current through the human body. The way the current passes through the human body plays a significant role in the outcome of the lesion, since the current can pass through vital organs: the heart, lungs, and brain. The influence of the current path on the outcome of the lesion is also determined by the resistance of the skin in various parts of the body. Possible current loops: arm-arm, arm-leg and leg-leg. The most dangerous are the head-arm and head-leg loops. while the respiratory organs and the heart are affected.
Type and frequency of electric current. Alternating current is 4-5 times more dangerous than direct current. This follows from a comparison of the threshold perceptible, as well as not releasing currents for alternating and direct currents. Cases of damage in electrical installations with direct current are several times less than in similar installations with alternating current. This provision is valid only for voltages up to 250-300 V. At higher voltages, direct current is more dangerous than alternating current.
For alternating current, its frequency also plays a role. With an increase in the frequency of the alternating current, the impedance of the body decreases, which leads to an increase in the current passing through the person, therefore, the risk of injury increases. The greatest danger is the current with a frequency of 50 to 1000 Hz; with a further increase in frequency, the danger of damage decreases and completely disappears at a frequency of 45-50 kHz. These currents maintain a risk of burns.
Individual properties of a person. It has been established that physically healthy and strong people endure electric shocks more easily. Increased susceptibility to electric current is different for people suffering from skin diseases, of cardio-vascular system, organs of internal secretion, lungs, nervous diseases. The safety rules for the operation of electrical installations provide for the selection of personnel for the maintenance of existing electrical installations for health reasons. For this purpose, a medical examination of persons is carried out upon admission to work and periodically once every two years in accordance with the list of diseases and disorders that prevent admission to maintenance of existing electrical installations.
Conditions of the external environment. The conditions in which a person works can increase or decrease the risk of electric shock. Dampness, conductive dust, caustic vapors and gases have a destructive effect on the insulation of electrical installations. The high temperature and humidity of the surrounding air lower the resistance of the human body, which further increases the risk of electric shock.
Depending on the presence of the listed conditions that increase the danger of current exposure to a person, the “Electrical Installation Rules” divide all premises according to the danger of electric shock to people into three categories: especially dangerous, with increased danger, without increased danger.
- 1. Particularly dangerous premises for the defeat of people by electric current are characterized by the presence of one of the following conditions that create a special danger:
- special dampness - 100% (ceiling, walls, floor and objects in the room are covered with moisture);
- chemically active or organic environment that destroys the insulation and current-carrying parts of electrical equipment;
- Simultaneous implementation of two or more conditions of increased danger. Baths, showers, underground storage rooms, etc. can serve as an example of such premises.
- 2. Premises with an increased risk of electric shock to people are characterized by the presence in them of one of the following conditions:
- Humidity exceeding 75%;
- conductive dust;
- conductive floors (metal, earthen, reinforced concrete, brick);
- · heat(above + 35C);
- · the possibility of simultaneous contact of a person with the metal structures of buildings and mechanisms that are connected to the ground, on the one hand, and to the metal cases of electrical equipment, on the other. Drilling rigs, oil pumping stations, workshops can serve as an example of such premises. machining materials, warehouse unheated premises, etc.
- 3. Premises without an increased risk of electric shock to people are characterized by the absence of conditions that create an increased or special danger. These include residential premises, laboratories, design offices, plant management, office space and others.
Protecting a person from electric shock. Protective measures in electrical installations. Electrical installations are a set of machines, devices, lines, auxiliary equipment (together with the premises in which they are installed) intended for the production, transmission, distribution of electrical energy.
The defeat of a person by electric current is possible only when the electrical circuit is closed through his body or, in other words, when a person touches the network at least at two points.
Touch voltage (Upr) is the potential difference between two points of an electrical circuit that a person touches at the same time. It happens:
- · at two-phase inclusion in a network;
- · when single-phase connection to the network (in contact with live parts of the equipment - terminals, tires, etc.);
- upon contact with non-current-carrying parts of the equipment that accidentally become energized due to a violation of the wire insulation;
- in the event of step voltage.
The current (J) flowing through the human body is
where Upr - touch voltage; Rh is the resistance of the human body.
The current can be reduced either by reducing the contact voltage (using low voltages) or by increasing the human resistance (using PPE).
With a two-phase inclusion of a person in the network, the touch voltage will be equal to the linear voltage. If a person touches an electrically damaged installation that has a ground, then the touch voltage will be lower than the voltage of this installation, since any grounding device reduces the potential of the electrical installation housing.
Step voltage is the potential difference between two points on the surface of the earth, on which a person is standing at the same time. The potential difference occurs when a bare wire falls to the ground or when approaching the ground electrode in the mode of current flowing through it.
The step voltage value (Ush) is determined by the formula:
where c is the potential at the point where the wire touches the earth; r is the radius of the conductor; a - estimated step length, equal to 0.8 m; x is the distance from the center of the conductor to the nearest leg of the person.
The higher the ground potential and the smaller the distance (x), the higher the step voltage value. Step tension practically disappears at a distance of more than 15-20 meters.
Safety when working with electrical installations is ensured by the use of various technical and organizational measures. They are regulated by the current Intersectoral rules for the operation of electrical installations (2001).
Technical means of protection against electric shock are divided into collective and individual.
The main collective methods and means of electrical protection:
* insulation of conductive parts (wires) and its
continuous control;
- * installation of protective devices;
- * warning alarm and blocking;
- * use of safety signs and warning posters;
- * application of low voltages;
- * protective grounding;
- * zeroing;
- * protective shutdown.
Insulation of wires, installation of protective devices, warning alarms and interlocks, as well as the use of safety signs and warning posters are related to protection against contact with live parts of installations.
Insulation of conductive parts is one of the main electrical safety measures. According to the PUE, the insulation resistance of the conductive parts of electrical installations relative to the ground must be at least 0.5 MΩ (1 MΩ = 106 Ohm.)
Distinguish between working and double insulation.
Working is insulation that ensures normal operation electrical installation and protection of personnel from electric shock.
Double insulation, consisting of working and additional, is used in cases where it is required to ensure increased electrical safety of equipment (for example, hand-held power tools, household electrical appliances, etc.).
There are basic and additional isolating means. The main insulating electrical protective equipment is able to withstand the operating voltage of electrical installations for a long time, therefore they are allowed to touch live parts under voltage. In installations up to 1000 V, these are dielectric gloves, tools with insulated handles, voltage indicators.
Additional electrical protective equipment has insufficient electrical strength and cannot independently protect a person from electric shock. Their purpose is to enhance the protective effect of the main insulating means with which they must be used. In installations up to 1000 V - dielectric boots, dielectric rubber mats, insulating stands.
Installation of protective devices. Uninsulated conductive parts of electrical installations operating under any voltage must be securely fenced or located at an inaccessible height to prevent accidental human contact with them. Structurally, fences are made of solid metal sheets or metal meshes.
Warning signals and blocking. To warn of the danger of electric shock, various sound, light and color signaling devices are used. In addition, the designs of electrical installations provide for interlocks - automatic devices that block the path to the danger zone. Interlocks can be mechanical (stoppers, latches, curly cutouts), electrical or electromagnetic.
Warning posters are used to inform personnel about the danger, which, in accordance with their purpose, are divided into warning, prohibition, permit and reminder. Parts of equipment that pose a danger to people are painted in signal colors. They are affixed with a safety sign in accordance with GOST 12.4.026 “Signal colors and safety signs”. Buttons and levers for emergency shutdown of electrical installations are painted red.
Application of low voltages. To reduce the risk of electric shock to people working with portable power tools and lighting lamps in especially dangerous rooms, a low voltage is used, not exceeding 42 V. In some cases, for example, when working in mine workings, a voltage of 12 V is used to power hand-held portable lamps. Sources low voltage are transformers, batteries, batteries of galvanic cells, etc.
When the current shorts to the metal parts of the equipment (short to the case), voltages appear on them that are sufficient to strike people. In this case, protection against electric shock can be carried out in three ways: protective grounding, grounding and protective shutdown. They are the protection of a person from the voltage that appeared on the case as a result of insulation failure.
Protective grounding is a deliberate connection to the ground of metal non-current-carrying parts of electrical equipment that may become energized if the insulation of the electrical installation is broken. Protective grounding is arranged in electrical networks with isolated and grounded neutrals.
If a short circuit occurs and the body of the electrical installation is energized, then the person who touches it falls under the contact voltage (Vpr), which is determined by the expression:
Vpr = Vz - Vx,
where Vz is the total voltage on the body of the electrical installation, V; Vx is the potential of the ground or floor surface, V.
The principle of operation of protective grounding is to reduce to safe values the contact voltages caused by a short circuit to the case.
All metal parts of electrical installations and equipment are subjected to protective grounding, for example, cases of electrical machines, transformers, lamps, switchboard frames, metal pipes and shells of electrical wiring, as well as metal cases of portable electrical receivers.
Structurally, the grounding device consists of metal electrodes (corner and metal pipes with a length of at least 2.5 m), interconnected by a metal strip, which is superimposed on the metal parts of the equipment. The number of ground electrodes depends on the electrical resistivity of the soil and the required value of the resistance of the ground loop.
Depending on the relative position of the grounding conductors and the equipment to be grounded, remote and loop grounding devices are distinguished. The first of them are characterized by the fact that the grounding conductors are placed outside the site on which the grounded equipment is located, or are concentrated on some part of this site.
A loop grounding device, the grounding conductors of which are located along the perimeter around the grounded equipment at a small distance from each other (several meters), provides a better degree of protection than the previous one.
Grounding conductors are artificial, which are used only for grounding purposes, and natural, which are used as pipelines located in the ground (with the exception of pipelines of flammable liquids or gases), metal constructions, rebar reinforced concrete structures, lead sheaths of cables, etc. Artificial ground electrodes are made of steel pipes, angles, bars or strip fabric.
Requirements for protective grounding resistance are regulated by the PUE. At any time of the year, this resistance should not exceed 4 ohms - in installations operating at voltages up to 1000 V (drilling rigs, oil pumping stations, etc.); if the power of the current source is 100 kV / A or less, then the resistance of the grounding device can reach 10 ohms.
Protective grounding is designed to protect personnel from electric shock in four-wire networks with a solidly grounded neutral up to 1000 V. Usually these networks are 220/127, 380/220 and 660/380 V.
Grounding is an intentional connection with a neutral conductor of metal parts of equipment that may be energized. The principle of operation of zeroing is the transformation of a short circuit to the body into a single-phase short circuit. The purpose of this is to induce a high current capable of providing protection operation and thereby automatically disconnecting the damaged installation from the supply network. Such protection can be: fuses, magnetic starters and automatic machines.
The response time of the protection elements depends on the current strength. So, for fuses and thermal automata, the fuse operation time is 0.1 s. Electromagnetic circuit breaker de-energizes the network in 0.01 s.
Protective shutdown is protection against electric shock in electrical installations operating under voltage up to 1000 V by automatic shutdown of all phases of the emergency section of the network within the time allowed by human safety conditions.
The main characteristic of this system is the speed, it should not exceed 0.2 s. The principle of protection is based on limiting the time of dangerous current flow through the human body. There are various protective shutdown schemes, one of them is based on the use of a voltage relay.
When a phase wire is closed to a grounded or grounded electrical installation case, a case voltage appears on it. If it exceeds a predetermined maximum allowable voltage, a protective shutdown device is activated. The operation of the protective shutdown circuit is presented in. Protective shutdown is recommended when electrical safety cannot be ensured by grounding or grounding, and also if these devices cause difficulties in use:
- * in mobile installations with voltage up to 1000 V;
- * to turn off electrical equipment remote from the power source, as an addition to zeroing;
- * in an electrified tool as an addition to protective grounding or grounding;
- * in rocky and frozen soils if it is impossible to perform the necessary grounding.
Organizational measures to ensure the safe operation of electrical installations. These include the execution of the relevant work by order or order, admission to work, supervision of the work, strict observance of the regime of work and rest, transitions to other work and completion of work.
An order for work in electrical installations is a task drawn up on a special form for safe production, which determines the content, place, start and end time of work, the necessary safety measures, the composition of the teams and persons responsible for the safety of the work. An order is the same task for the safe production of work, but indicating the content of the work, place, time and persons entrusted with its implementation.
All work on the conductive parts of electrical installations under voltage and with de-energization is performed in parallel, except for short-term work (lasting no more than 1 hour), requiring the participation of no more than three people. These works are carried out according to the order.
Organizational measures also include training of personnel in the correct methods of work with the assignment to employees servicing electrical installations of the appropriate qualification groups.
Providing first aid to a person affected by electric shock. First aid to a person struck by electricity consists of two stages: releasing the victim from the effects of electric current and giving him first aid.
If a person has touched the conductive part of the electrical installation and cannot independently free himself from the effects of current, then those present must help him. To do this, quickly turn off the wiring using a switch, knife switch, etc. If it is impossible to quickly disconnect the electrical installation from the network, then the person providing assistance must separate the victim from the conductive part. It should be borne in mind, however, that without necessary measures precautions, you should not touch a person who is in the current circuit, as you yourself can get under voltage.
If the victim has come under the action of voltage up to 1000 V, the conductive part can be separated from him with a dry rope, stick or board, or the victim can be pulled by the clothes if it is dry. The hands of the person providing assistance should be protected with dielectric gloves, legs should be put on rubber shoes or stand on an insulating stand (dry board).
If the above measures did not work, it is allowed to cut the wire with an ax with a dry wooden handle or cut it with another tool with insulated handles.
At a voltage exceeding 1000 V, the persons providing assistance must work in dielectric gloves and shoes and pull the victim away from the wire with special tools designed for this voltage (rod or tongs). It is also recommended to short-circuit all power line wires by throwing a wire connected to ground over them.
After the release of the victim from the effects of electric current, he is given first aid. If the person who received the electrical injury is conscious, he must be provided with complete rest until the arrival of a doctor or urgently taken to a medical facility.
If a person has lost consciousness, but breathing and heart function are preserved, the victim is placed on a soft bedding, the belt and clothes are unfastened, thereby ensuring the inflow fresh air. Next give a sniff ammonia, | rub and warm the body. With rare and convulsive, as well as deteriorating breathing, the victim is given artificial respiration. In the absence of signs of life, artificial respiration is combined with external heart massage.
Questions for self-control
What effect does electric current have on the human body?
What is electrical injury?
What are the causes of electrical injury?
What factors affect the outcome of electric shock?
Describe the permissible levels of electric shock?
List the main cases of connecting a person to the power grid.
What is step voltage?
List the main methods and means of electrical protection and describe them?
Classification industrial premises according to the degree of danger of electric shock.
What is protective grounding and how is it used to protect a person from electric shock?
What is zeroing and what is the principle of ensuring electrical safety with its help?
What is a safety shutdown and how does it work?
What are the personal protective equipment against electric shock?
Logvinenko Lyudmila Viktorovna, teacher-organizer of OBZH MBOU "Smorodinskaya secondary school" Graivoronsky district, Belgorod region
Life safety lesson in grade 5 on the topic: “Beware of electricity!”
Self-analysis of the topic of the lesson. According to statistics, recently there have been many cases of electrical injuries in everyday life due to non-compliance with the rules for the operation of electrical household appliances. Particularly susceptible to electric shock are children who know little about the danger that awaits them while playing near power facilities. This topic relevant at any age and at any time of the year, but it is especially important to repeat the electrical safety rules before the holidays. After all, children often stay at home alone during the holidays and use electrical appliances on their own, without adult supervision. This lesson was held before the autumn holidays and contributed to the actualization of students' knowledge about the correct handling of electrical appliances and the rules of conduct near power facilities.
Subject:"Caution - electricity!"
Lesson Objectives:
1. Create conditions for the generalization and expansion of schoolchildren's knowledge about electricity.
2. Organize the activities of students to repeat the rules for the safe handling of electrical appliances.
3. Contribute to the development of a safe lifestyle, the desire to take care of their health and the health of their loved ones.
Lesson type: generalization and systematization of knowledge.
Lesson plan:
What will be discussed?
Electricity: friend or foe?
What is it like?
How does it hurt a person?
How to avoid it?
How not to get hurt during a thunderstorm?
Who are they - amazing and dangerous animals?
Equipment: laptop, multimedia equipment, “Safe Travel” presentation, electrical safety warning signs, pictures of electrical appliances, “Electrical Safety” crossword puzzle, electrical test, reminders for parents.
During the classes:
Organizing time. Good afternoon guys! I'm glad to see you at the OBZh lesson. I wish you good luck and Have a good mood. Smile at your neighbor. May everything work out for you. (slide 1 - Appendix 1)
Formulation of the topic of the lesson and setting the objectives of the lesson. See what these drawings have in common? (slide 2) What will be discussed in the lesson? Indeed, the topic of our lesson is “Beware of electricity!” (slide 3)
Actualization of students' knowledge
What role does electricity play in our lives? Think electricity is friend or foe? (slide 4)
Why is electric current dangerous? What are the consequences of electric shock to a person? (slide 5)
What is the characteristic of electric current? (slide 6)
Can a person detect an electric current in advance? How to warn a person about the danger of electric shock? (slide 7) Where can you see such signs? Where did you see such signs at school? (Annex 2)
Remember what electrical safety rules on the street do you know? (slide 9)
Power facilities are air and cable lines transmission lines, substations, transformer substations, distribution points.
Rules of conduct near power facilities
Do not go into transformer boxes and electrical installations.
Do not throw anything on the wires or play near them.
Don't steal or help steal electrical wires.
Don't climb on the supports.
Do not approach broken wires closer than 8-10 meters.
Learning new material.
Teacher's explanation. Do you know why it is impossible to approach broken wires closer than 8-10 meters? Do you want to know the correct answer?
Pay attention to the picture on the slide (slide 10). The danger zone is marked with circles. There is a risk of electric shock if exposed to "step voltage"- this is the voltage that occurs when a wire breaks and falls to the ground of an existing power line of 0.4 kV and above. The current flow path does not stop unless the power line has been disconnected. The earth is a conductor of electric current and becomes, as it were, a continuation of the power transmission wire. Any point on the surface of the earth, located at the spreading point, receives a certain potential, which decreases as it moves away from the point of contact of the wire with the ground. Electric shock occurs when a person's feet touch two points on the ground that have different electrical potentials. Therefore, step voltage is the potential difference between two points of contact with the ground, the wider the step, the greater the potential difference and the more likely an electric shock.
Familiarity with the rules of "step voltage":
DO NOT run or approach a lying wire or a person on the ground by running or walking!
DO NOT lift your soles off the ground and take big steps!
You should only move with a “goose step” - the heel of the walking leg, without leaving the ground, is attached to the toe of the other leg.
It is UNACCEPTABLE to touch the victim or metal objects without first de-energizing!
Turn off the electricity as soon as possible using a switch, breaker, unplug, etc.
3. Practical work: working out the "goose step". Stand up and show how to goose step - the heel of the walking leg, without leaving the ground, is attached to the toe of the other leg.
Fizminutka. Didactic game"No Rule for Electrical Appliances"(slide 11).
Drawings of electrical appliances are hung in the classroom: washing machine, microwave, iron, hair dryer, vacuum cleaner, etc. Students need to stand up, take a drawing and name the rule for operating the device, which begins with the words cannot. The one who sits at the table last will lose.
Generalization and systematization of students' knowledge.
Rules of conduct during a thunderstorm. Look at the picture. What is shown on it? (lightning bolt) How does it relate to the topic of our lesson? Remember the rules of conduct during a thunderstorm. (slide 12)
It's interesting and dangerous.(slide 13) Name the animals shown in the picture. An electric eel generates more than 500 watts of electricity, and an electric stingray up to 300 watts. The energy generated by the ramp is enough to start the engines of 50 cars.
Solving a problem situation.
Reading a poem:
What are sockets for?
Adults and children know:
We always insert into them
From wire appliances.
foreign gizmos
(Everyone should be clear!)
Nails, studs, needles, knitting needles
It's dangerous to stick in them!
But what about small children who do not yet know the rules? (slide 14) Advice for parents with small children: cover sockets or install safe sockets.
Checking the studied material.
Collective work. Solving the crossword puzzle "Electrical safety". (Annex 3)
Crossword questions:
Running without legs
Burning without fire
No teeth, but bites. (Electricity)
Hanging pear - you can not eat. (bulb)
Which hands should not touch electrical appliances? (wet)
What can't you stand under during a thunderstorm? (tree)
What can not be done during a thunderstorm? (bathe)
What is the current like when it is angered? (wicked)
Individual work. Testing. Perform an electrical test. Check yourself. (slide 16) (Appendix 4)
Grading a lesson.
Summary of the lesson.
What will you tell your parents at home? What have you done before and won't do after this lesson?
Homework
Draw a rule for electrical safety.
Tell parents about electrical safety. (Annex 5)
Reflection
Guys who have learned the rules well and will not break them, attach a warning sign “Caution - electricity” to the thunderstorm drawing (Appendix 6)
Bibliographic list
Electrical Safety Rules of OAO Belgorodenergo "On Electricity for Children".
Materials of the competition of video lessons on the prevention of electrical injuries "The best electrical safety lesson".
JSC "Altaienergo" website.
This lesson development is intended for students in grades 4-6. It can be used by OBZH teachers, primary school teachers and class teachers when repeating electrical safety rules before the holidays. The proposed material contributes to the actualization of students' knowledge about electricity, the rules for handling electrical household appliances, rules of conduct near power facilities, during a thunderstorm.
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slide 1
Electricity, life safety, primary classes, S.A. Selivanova, 2012
slide 2
How do electrical appliances work?
I run along the paths
I can't do it without a path.
Where am I not guys
Lights won't turn on in the house
To distant villages, cities
Who is on the wire?
bright majesty
It's ELECTRICITY!
Bubbling water flows in the river,
Electric current flows through the wires.
Goes, runs, flies to help us
Cook dinner, vacuum the floor, the sofa.
slide 3
Electricity is supplied to electrical appliances using sockets and plugs.
- SOCKET
- FORK
slide 4
IRON
Strokes everything it touches
And if you touch it, it bites.
A very necessary friend in life -
Electric iron!
slide 5
hair dryer
The dry wind dries Curls of my mother.
slide 6
FRIDGE
Love, look:
North Pole inside
There sparkles snow and ice,
Winter lives there.
Forever us this winter
Brought from the store.
Slide 7
ELECTRIC KETTLE
Boiling from the inside
And blows bubbles.
enjoy the evening
Delicious brewed tea!
Slide 8
TELEPHONE
Slide 9
TV
I look at the screen in the apartment,
And I see what's going on in the world.
Weather, news, movies,
Learn about sports at the same time.
Slide 10
WASHING MACHINE
Item needed
we have
Works silently
he pleases the eye.
It will save time
and save your hands
Washing machine
save us from worries!
slide 11
VACUUM CLEANER
We have a robot in our apartment, -
He has a huge trunk.
The robot loves cleanliness
And buzzes like a liner: "Too-oo."
Willingly swallows the dust
But not sick, not sneezing.
slide 12
ELECTRIC STOVE
four red suns
I have in my kitchen
four red suns
They burned and faded.
Borscht, pie, pancakes are ready.
Until tomorrow the sun is not needed.
slide 13
MICROWAVE
Cooking quickly, deftly -
Need a microwave.
Ring! Here is delicious food.
We cook quickly, without difficulty!
Slide 14
RECORD PLAYER
My friend is with me
lives nearby.
Click on the button -
and he will sing a song.
slide 15
FAN
With propeller fast this
He gives us a fresh breeze!
And the air will be fresher
For all people, for all children!
slide 16
Slide 17
Doesn't like electricity
- METAL
- ITEMS
Slide 18
Think. Draw a conclusion
Slide 19
Can I repair electrical appliances myself?
Slide 20
Why is there a danger sign?
slide 21
Consider the drawing carefully.
Make a conclusion.
slide 22
State the cause of the fire
slide 23
Rules for the use of electrical appliances
- Do not turn on electrical appliances with wet hands.
- Bare wires must not be touched.
slide 24
Continue the offer
Today in class I (me) ....
Slide 25
View all slides
Abstract
Lifestyle lesson
Primary classes
"Electricity"
Target:
Tasks:
Lesson progress
Conducting an experiment.
(action of electricity)
Topic message.
Story(handout on tables)
supports,
lightning rod.
electrical substation. There is a special car - transformer.
How does electricity come to your home?
(Discussion.)
Crossword "Electrical appliances"
Only me, only me
I'm in charge of the kitchen.
Without me, no matter how hard you work,
He willingly inhales the dust,
On the table, in a cap,
Yes in a glass bottle
A friend settled
Cheerful spark. (lamp)
Look at my barrel
The top is spinning in me
He doesn't hit anyone.
pull themselves apart
Not radio, but says
Do not use faulty electrical appliances.
You can not repair, disassemble electrical appliances yourself.
Do not pick the socket with your finger or other objects.
(discussion)
Outcome.
Reflection
Continue the offer.
Today in class I (me) ....
Lifestyle lesson
Selivanova Svetlana Anatolievna
Primary classes
"Electricity"
Target:
Familiarize students with the rules for using electrical appliances.
Tasks:
To expand students' knowledge about the variety of electrical appliances used in everyday life.
Familiarize yourself with the rules for using electrical appliances.
Develop logical thinking.
Build information skills.
Lesson progress
Conducting an experiment.
If you rub a pencil on a piece of woolen cloth, then bring it to small pieces of paper laid on the table, we will see .... What is this phenomenon?
(action of electricity)
Topic message.
The word "Electricity" is a Greek word and means amber. Even in ancient times, the Greek mathematician Thales had an idea about electricity. By rubbing the amber stick against the wool, he seemed to charge it with static electricity. Brought to the head, this wand attracted the hair. We have received such electricity ourselves.
But this electricity is called static because it only accumulates in various objects. It cannot be transmitted over a distance and used in lighting fixtures.
Later, scientists found that electricity is a stream of tiny charged particles - electrons. Each electron carries a small charge of energy. But when there are a lot of electrons, the charge becomes large and an electric voltage arises. This is why electric current can travel long distances through wires.
Independent work in groups. Find the answer to the question:
Story(handout on tables)
To transfer electricity to where it is needed, power lines are built. You, of course, saw high pillars outside the village - supports, to which wires are attached. Through these wires, electricity from power plants comes to different cities and towns.
Electricity flows through wires high voltage reaching hundreds of thousands of volts.
So that no one could even accidentally touch the wires, they are suspended high in the sky on special supports. And so that lightning does not strike the wires, a special wire is hung over them - lightning rod.
You can see it at the very top of the pillar.
When electricity comes to the city through wires, it goes to electrical substation. There is a special car - transformer.
Never touch a cable that is sticking out of the ground, because it may be under high voltage!
Electricity comes through the cables to the transformer box, which stands near the houses in your village. The small transformer in it lowers the voltage even more, so that the electricity can now be used in various appliances that are in your home.
How does electricity come to your home?
Why are the pillars so high?
What rule did you learn from reading the story?
(Discussion.)
What appliances in your home can use electricity?
Crossword "Electrical appliances"
Only me, only me
I'm in charge of the kitchen.
Without me, no matter how hard you work,
Sit without lunch. (electric stove)
He willingly inhales the dust,
Not sick, not sneezing. (vacuum cleaner)
On the table, in a cap,
Yes in a glass bottle
A friend settled
Cheerful spark. (lamp)
Look at my barrel
The top is spinning in me
He doesn't hit anyone.
The cream will knock you down quickly. (mixer)
pull themselves apart
Not radio, but says
Not theater, but shows. (TV)
What was the keyword? (dangerous)
When you press the switch of a lamp or some device, the electric current coming from the generator begins to flow through the wires and the device starts to operate, and the light bulb glows.
If the wires fail, the electricity becomes dangerous. A person can accidentally touch a bare wire, and he will be shocked. Wires can be connected and a short circuit or even a fire will occur.
Therefore, if you see a bare wire or a faulty switch, an outlet, immediately tell an adult about it.
Everything that runs on electricity must be serviceable!
If the TV or vacuum cleaner smells of burning, if sparks are visible, you must immediately unplug the wire from the outlet. This device needs to be repaired.
Can you repair faulty electrical appliances yourself?
You need to know how to handle electricity!
What should never be done?
Do not use faulty electrical appliances.
You can not repair, disassemble electrical appliances yourself.
Do not pick the socket with your finger or other objects.
Remember, electricity does not like being near water.
Discuss pictures on slides. (We draw our own conclusions)
Several electrical appliances are on the table.
Consider them carefully and determine which electrical appliances cannot be used.
(discussion)
Outcome.
Let's repeat once again what rules for using electrical appliances.
What have we learned about electricity?
Why is it dangerous? How to avoid trouble when interacting with electricity?
Reflection
Continue the offer.
Today in class I (me) ....
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