A message on the topic of electricity. Summary of a lesson on life safety in the preparatory school group “Magic Electricity”
Subject:Game-activity "His Majesty Electricity"
Target:
studying safety rules and fire safety when using electrical appliances in the house.
Tasks:
Educational:
identify areas of increased danger in the house that arise when rules for handling electrical appliances are violated;
introduce and study safety rules when using electrical appliances at home;
to instill the skills and abilities to act in the event of a fire when operating electrical appliances at home;
Corrective:
develop dialogical speech through question-and-answer form,
enrich and activate children's vocabulary using words: instructions, electricity, electrical appliance, fire hazards, vacuum cleaner, electric meat grinder, mixer, toaster, computer, microwave oven, bread slicer, juicer, vegetable cutter, coffee grinder, coffee maker; practice pronunciation of words with a complex sound-syllable structure;
develop coordination of movements through physical exercises,
Educational:
instill in children a sense of careful handling of electrical appliances; prevent accidents at home,
cultivate a conscious attitude towards issues of personal safety in the home,
Equipment.
The teacher has pictures, illustrative materials (slides).
Students have colored pencils or markers.
PROGRESS OF THE CLASS
Org. moment.
Psycho-gymnastics - “A minute of kindness”
“In one village, people knew how to give each other good things.
Do you know how? - very simple:
When they extended their palms to each other, a small spark, a small, small sun, flashed between them.
So small that it did not burn, but only warmed the palms and flashed with bright sparks.
Let's look into each other's eyes with warmth,
Let's smile at each other and say:
I love you…
I love me…
I love everybody…
Stage 1. Update knowledge
We love our home very much,
Both cozy and dear.
But not everyone could
Redo a lot of things.
We need to clean the house,
Cook, wash,
And also iron the clothes...
How to cope with all the work?
And it’s wonderful that now
We have helpers.
They make our work easier
They save our time.
And they are brothers,
Powered by electricity.
Everyone understands and without dispute,
These are electrical appliances.
Household appliances are ours faithful helpers. These are complex devices that are powered by electricity and perform a wide variety of household tasks. Some wash clothes, others help in the kitchen, others collect dust, others store food, etc. Electrical appliances save our time and energy.
(- Let's solve the crossword puzzle "Electrical appliances")
Crossword "Electrical appliances"
1. He puffs like a locomotive
It is important to keep your nose up.
Make some noise, calm down -
Invite the seagull to have a drink. (Samovar)
2. I inhale a lot of dust
May you be healthy. (Vacuum cleaner)
3. There is a button on the head,
There is a sieve in the nose, one hand,
Yes, and the one on the back. (Kettle)
4. They stuffed her mouth with meat,
And she chews it.
Chews and chews, but does not swallow -
Sends it to the plate. (Meat grinder)
5. No ears, but hears;
I have no hands, but I write. (Record player)
6. A very smart car.
She will help you write,
And draw
And even translate it into another language. (Computer)
Guys, what do we call all these devices? – electrical appliances
– What do all these objects have in common? (Electrical household appliances).
– Why do people need electrical appliances? (Man invented all these devices for his convenience.)
Game “What is an electrical appliance for?” - 2 teams for the correct one the answer is a light bulb
An electric lamp is needed to provide light.
2. A refrigerator is needed to store food.
3. A vacuum cleaner helps clean the apartment and removes dust.
4. The washing machine is designed for washing clothes.
5. Iron – for ironing clothes.
6. Electric stove - for cooking.
7. Electric kettle – for boiling water.
8. Microwave oven - for cooking and heating food.
– Do you think all these electrical appliances can be dangerous?
- crossword entry - what happened - the word - dangerous
Conclusion: Very often the person himself becomes the culprit dangerous situations, i.e. he creates them himself.
– We continue the series of classes “Sections of safety and human protection in emergency situations.” Today we will talk about safety in the house where each of us lives, and about the most common things in our home. Every house is more than just a roof and walls. The man filled his home with convenient mechanisms. There are many things in every person's home, some of which are household appliances and electrical appliances. All these things are our helpers, they help a person, create convenience in our lives. Our conversation will touch on a very serious topic, namely, safety in your home when using electrical appliances.
- Guys, I will name the devices, and you will explain in what cases they are dangerous.
electric kettle (turned on without pouring water into it, plugged into a faulty socket, turned on wet hands, they forget to turn it off after the water has boiled in it)
electric iron (left on unattended, similar to the first)
washing machine (turned on without parental permission, open the lid while the machine is running, similar to the first)
Stage 2. Historical reference
Conversation about the benefits of electricity
– Why do people really need electricity, what does it give people? (Electricity gives people light in the house).
- Guys, you probably know from books, from the stories of your grandmothers, how people used to light their rooms? (People used candles, kerosene lamps, torches, lamps)
– What powers electrical appliances? (Current).
– Where does electricity come from to houses? (From power plants)
– Where does electricity live in each house? (In sockets)
– Can I touch the sockets with my hands? (No)
– How and why does electricity flow from the outlet to electrical appliances? (By wire)
– What needs to be done for them to start working? (Include in electrical outlet)
Let's guys now show how current flows through wires, let's play a game.
Game "Current Runs Through Wires"
Imagine that you are small particles of current that run through wires. (Children pick up a rope with knots, intercepting the knots on the rope with their right and left hands, say the words)
Current runs through the wires
Light brings light into our apartment.
For the devices to work,
Refrigerator, monitors,
Coffee grinder, vacuum cleaner,
Current carries energy.
(Last child raises his hands up).
Stage 3. Group assignment
– For the correct answer, the team receives points - light bulbs. Each team gets its own light bulbs.
Cards with views of the apartment.
Find sources of increased danger and circle them with a red marker.
Result: counting the number of light bulbs.
Guys, we are electricity - let's call His Majesty - it is the most important thing in our house - apartment
– What opportunity does electricity give us in the house? ( Using various electrical appliances)
There are many electrical hazards in our home.
Stage 4.
– Very often a person himself becomes the culprit of dangerous situations, i.e. he creates them himself. To maintain your health and life, you need to know the rules of use well. and promptly eliminate the reasons why potential dangers may turn into real ones.
Therefore, it is necessary to follow a set of rules when using home electrical appliances, what are such instructions called?
Instructions(instruction) - a set of rules establishing the order and method of carrying out, doing something...Each electrical appliance has its own instructions - but the basic rules are the same for all, which you must always remember………
– Name the fire extinguishing means for electrical appliances in the house? ( Water, thick fabric, blanket, clothes, earth from flower pot, fire extinguisher).
Bottom line: basic safety rules.
– Now let's look at the posters that will once again remind you of what rules you need to follow in everyday life to avoid electric shock! These rules are useful for both children and adults to know, so after our lesson I recommend that you tell your parents about some of them!
reading the rules
Before starting work, check the serviceability of the cord (cable), wires, and the reliability of the switch!Be careful! Do not use household electrical appliances and lamps outdoors.
Attention! Don't put yourself in danger! Be careful! Do not use household electrical appliances with damaged insulation.Children! Do not insert any objects other than a plug into the sockets! Remember about the dangers of electric current and follow basic electrical safety rules at home.
– These are the rules that will help you avoid the danger that is fraught with the bright Majesty – Electricity!
Stage 6. Teacher's story about electric current, high voltage and about measures in case of electric shock.
– There are many electrical hazards in our house. Why is electricity dangerous? (Electric shock)
– To protect yourself from electric shock, remember:
do not touch exposed or poorly insulated wires;
do not use faulty electrical appliances;
Do not touch a switched-on electrical appliance with wet hands.
– Guys, we were able to verify once again that ELECTRICITY is very important for us, that we cannot modern world do without electricity, which must be respected and protected. We cannot see electricity. Therefore, the electric current running through the wires, despite the fact that it is so necessary for a person, very dangerous! People who work with electricity warn us about this, putting their lives in constant danger. Guys, do you know the name of the profession of people who work with electricity? – electrician
The effect of electric current on the human body.
If a person, through his negligence, comes under the influence of electric current, his central nervous system is paralyzed. nervous system. The current strongly “attracts” to itself, preventing it from “breaking away”. The person has difficulty breathing and the heart may stop. The man dies. If the person survives, they may be left with severe burns for life.
According to statistics, accidents with children occur most often in the summer. Electric current poses a particularly serious threat to health and life. Dangerous tension has already begun with 36 volts. At home and on the street we are surrounded by live wires and electrical equipment. 220 volts and above. This means that even the current that flows through the wires in your apartment is many times greater than the lethal one.
As a rule, electrical installations are marked with special warning signs or appropriate posters. They warn a person about the danger of electric shock, and it is unacceptable to neglect them, much less remove and tear them off.
Fizminutka:
everything I say, you show with your movements
The lights are on,
The teapots are puffing,
Irons are ironed,
Pies are being baked.
Game situation No. 1
Your TV lights up. What should your actions be?
Answer:
cover with a damp cloth;
turn off the TV;
call “101”.
Situation No. 2
The oil in the frying pan caught fire. What should your actions be?
Answer:
Place a damp towel over the pan and remove from the stove.
turn off the oven and cover the pan tightly with a lid
Fill the pan with water.
Situation No. 3
Your clothes caught fire. What will you do?
Answer:
fall to the floor;
cover with a damp cloth;
Situation No. 4
Imagine that you are left alone at home and decide to iron your clothes, when suddenly the iron cord flashes and sparks. Your actions:
run for water and douse the flames
unplug the cord and plug from the outlet
take the iron and remove it from the burning item.
Situation No. 6
If you were cut off by fire in an apartment on the fifth floor (no phone), what would you do?
I will call for help
I'll make a rope out of twisted sheets and climb down.
I'll plug the cracks in with wet towels and sheets. doorway Having reduced the flow of smoke, I will call for help through the window.
Situation No. 5
There's a fire in the house that you can't put out. What to do?
hide
call the firefighters.
cover your mouth and nose with a wet handkerchief and move towards the exit, pressing yourself to the floor
Result: It is necessary to act correctly, without panic, the speed of fire extinguishing and human safety depend on this
Game “Say the Word”
1. Heats water - a boiler
Cools - … (fridge)
2. Our oven retired
Will replace the old lady... ( microwave).
3. Forgotten skis, bike -
We watch day and night... (TV)
4. Every day we ring a bell -
Oh, our chatterbox … (telephone)
5. We quickly screwed in the lamp -
Ours shines again … (chandelier).
- light bulb for the correct answer
Game "Kitchen Helpers"(formation of complex words)
Bread cuts - Bread slicer.
Coffee grinds - Coffee grinder.
Brews coffee - Coffee maker.
Chopping meat - Meat grinder.
Vegetables are cut using a vegetable cutter.
Squeezes juice – Juicer.
Result: It is necessary to act correctly, without panic, the speed of fire extinguishing and human safety depend on this.
Stage 8 - final
1 team.
Team 2- You are given a card with a task: connect the beginnings of phrases with their endings, and you will get the rules of fire safety and actions in case of fire.
Summing up the competition(counting the number of light bulbs).His Majesty Electricity has prepared a gift for you - Safety and fire safety instructions when using electrical appliances
Thank you to His Majesty Electricity for the gifts that will help the children in their Everyday life.
Guys, each of you for your knowledge in the series of lessons “On the safety and protection of people in emergency situations” is awarded by His Majesty Electricity with a diploma of life safety
Lesson summary
– Today we devoted our lesson to considering situations in which danger may arise in everyday life. We wrote down instructions on the rules for handling electrical appliances, fire safety rules. Violation of safety rules can lead to irreparable consequences. The worst thing is that ignorance or inability to act correctly in certain situations can create a threat to human life and health. I wish everyone good health and hope that our classes will help you grow up as happy and successful people.
Class: 5
Presentation for the lesson
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Target. At the end of the lesson, students should:
Why is electricity dangerous and what does it mean?
How to protect yourself from electric shock;
b) have an understanding of electrical injuries,
c) developing interest in the subject,
d) education of safe behavior.
Study questions.
1. Dangers arising from violation of the rules for handling electrical devices and equipment.
2. Safety rules when using electrical appliances.
Equipment: presentation for the lesson, textbook, didactic and handouts
During the classes
1. Organizational point:
(On the screen Good morning! (Slide No. 1))
Well, check it out, my friend,
Are you ready to start the lesson?
Is everything in place?
Is everything alright:
Pen, book and notebook?
Is everything sitting correctly?
Is everyone watching carefully?
Let it be useful for the guys,
Our lesson is very important.
2. Updating knowledge (checking homework)
On the tables is a printed version of the “Dominoes” task.
We continue to talk about the dangers that we may encounter at home.
Section 2. Dangerous situations in the apartment (house).
And first, we will check with you how you coped with your homework. Annex 1
(Duplicated on screen).
Task: “Dominoes”. (Slide No. 2) the answers are recorded in the workbook.
U: Let's check what you got. (Slide No. 3)
Answers: 1d., 2a., 3c., 4b., 5d.
The teacher writes down the correct answers on the board and comments.
Students compare the results obtained with assessment criteria in points and independently evaluate themselves.
U: Well done!
Now pay attention to the screen. (Slide No. 4)
(Excerpt from the cartoon series “Lessons in caution with a smart owl”)
3. Statement of the topic and purpose of the lesson.
(Discussion of the passage and setting the topic of the lesson and determining the objectives of the lesson.)
U: What is the cartoon about?
D: About household appliances; about dangers at home
U: Why are they dangerous?
D: They all cause dangerous situations. Powered by electricity.
U: Right. These are electrical appliances and they run on electricity.
U: Electricity is one of the most striking discoveries of mankind. Very quickly it has become so familiar that we don’t notice it.
U: Based on the above, try to formulate the topic of the lesson. Write in a notebook.
(Slide No. 5)
The topic of our lesson: Electricity.
U: What should we know about electricity?
- Why is electricity dangerous?
- How to protect yourself from electric shock
Children record the topic of the lesson and goals in their workbooks.
Problem situation (slide No. 6)
T: Pay attention to the screen. We are faced with a very serious task and during the lesson we must solve it with you
Is electricity a friend and/or enemy of humans? (Appears on screen)
D. children's answer with examples.
U. Please note, opinions differ. Let's find the answer to this question together.
And first, tell me, in what cases does electricity become a source of danger for humans?
D: list possible dangerous situations.
U: The first step to solving our problem will be to work in groups of permanent members.
Work in groups - solving situational problems:
Assignment: For what reason does electricity become dangerous to humans?
The answer to each problem is one of the reasons
Reasons for duplicated images on the screen during scanning . (Slide No. 7)
Children write down the reasons in a notebook.
U. What can result from improper handling of electricity and electrical appliances?
D. Children's answer.
U. Is it correct to get an electrical injury? (Duplication on the board and on the screen) (Slide No. 8)
Electrical injury is damage to body tissue caused by electric current.
Passing through the human body, the current can cause muscle contraction, resulting in ruptures of blood vessels, skin, ligaments, and even dislocations of joints and bone fractures. The most dangerous thing in this case may be loss of consciousness with disturbance of cardiac activity or breathing, and the most tragic – cessation of breathing and blood circulation and lead to the death of a person.
Physical exercise.
U: Look at the screen and try to answer the question: how to protect yourself from electric shock? This will be the next step in solving our problem.
(Slide No. 9) an excerpt from the cartoon series “lessons of caution with a smart owl.”
U: What dangerous situations happened to the hero and for what reason?
T: How to protect yourself from electric shock?
D. children's answers are formulated and duplicated on the screen. (Slide number 10)
1. Do not touch exposed wires.
2. Do not use faulty electrical appliances.
3. Do not touch a switched off electrical appliance with wet hands.
4. Observe safety precautions when handling electrical appliances.
Write down the rules of caution in your notebook.
5. Reflection.
T: So are you ready to solve the most important task of our lesson?
U. Tell me, children: Is electricity a friend and/or enemy of man? And why? (Appears on screen) (Slide No. 11)
Of course, electricity is man’s friend and enemy!
After all, electricity provides us with modern lighting, heating, water supply, work, computers, television, cooking, industrial production. In a word, we live in a world of electricity. But we shouldn’t forget that electricity can cause dangerous situations for people if we don’t follow the personal safety rules that we talked about today?
6. Summing up the lesson.
1. What danger comes from electricity?
2. What is electrical trauma?
3. What rules should we follow to protect ourselves from electric shock?
7. Homework. On the desk:
Topic “electricity” pp. 36-39 questions orally.
Page 39. Problem 7.
Your younger brother put his hand on the wire of the turned on tape recorder and got an electric shock. The wire remained in your brother's hand.
Choose your next steps from the proposed options and determine their order by checking yourself with the material in the textbook:
- Grab the wire and pull it out of your brother's hands.
- Come and see how he feels.
- Turn off the lighting in the electrical panel.
- Pull the wire out of the socket using a dry wooden stick.
- Call an ambulance.
- Call your parents (neighbors).
The electrical saturation of modern geological exploration production (electrical installations, instruments, units) creates an electrical hazard. When working with electrical installations in production and household appliances, electrical safety requirements must be observed. They represent a system of organizational and technical measures and means that protect people from the harmful and dangerous effects of electric current.
When carrying out geological exploration work, 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 line 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. The neutral wire of the network, according to the PUE, is connected to the ground loop at at least 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, electric current causes thermal, electrolytic and biological effects.
The thermal effect of the current manifests itself in burns of the body, heating the internal organs of a person (blood vessels, heart, brain) to a high temperature.
The electrolytic effect of current is manifested in the decomposition of organic body fluids (water, blood) and disturbances in their physical and chemical composition.
The biological effect of current manifests itself as irritation and excitation of living tissues of the body and is accompanied by involuntary convulsive contractions of 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 treatable, although the severity can be significant, including death. The following electrical injuries are distinguished:
- 1) electrical burns;
- 2) electrical signs;
- 3) metallization of the skin;
- 4) electroophthalmia;
- 5) mechanical damage.
Electrical burns occur when there is significant voltage and imperfect human contact with live 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 of the smallest particles of metal, graphite, into the upper layers of the skin. The pain is caused by the heating of these particles.
Electroophthalmia - eye damage caused by intense radiation electric arc(ultraviolet and infrared rays are harmful).
Mechanical damage occurs as a result of sharp involuntary convulsive muscle contractions, including ruptures of the skin, blood vessels, dislocations of joints and bone fractures. Secondary consequences caused by a fall from a height or involuntary blows are possible.
Electric shock is the result of the biological action of current. 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 breathing, heartbeat and the onset of electric shock. At clinical death a person has no signs of life (no breathing or heartbeat), but life in the body has not extinguished and is maintained at a low level for 6-8 minutes. If you do not begin to revive the body, then the death of cerebral cortex cells (neurons) that are very sensitive to oxygen starvation occurs. With the expiration of the specified time, biological death may occur.
Factors that determine the risk of electric shock. The nature and consequences of exposure to electric current on a person depend on the following factors:
- · electrical resistance of the human body (Rh);
- · voltage (E) and current (J) values;
- · duration of exposure to electric current (t);
- · current paths through the human body;
- · type and frequency of electric current;
- conditions external environment;
- · individual properties of a person.
Electrical resistance to current is provided mainly by the skin, and in its composition is 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 used equal to 1000 Ohms. Damage to the stratum corneum (cuts, scratches, abrasions) reduces the body's resistance to 500-700 Ohms, which proportionally increases the risk of electric shock to a person. Moisturizing or contaminating the skin at elevated temperatures, which causes increased sweating, has the same negative meaning. The skin of the face, neck, and armpits has the least resistance, and vice versa, the skin of the palms and soles have increased resistance. With an increase in the duration of voltage, current and frequency, the resistance of the skin drops sharply, which aggravates the consequences of the passage of current through the human body.
Current magnitude and voltage. The main factor determining the outcome of electric shock is the strength of the current passing through the human body. Current strength is the amount of electricity passing through the human body per unit time. The greater the current, the more dangerous its impact. There are three stages of the effect of current on the human body and three threshold values corresponding to them: palpable, non-releasing and fibrillation.
A noticeable current causes noticeable, low-painful irritation. A person can independently free himself from a wire or live part that is energized. If a person is under the influence alternating current industrial frequency (f = 50 Hz), it begins to sense the current flowing through it when its value reaches 0.6-1.5 mA. For DC this threshold value is 6-7 mA.
The non-releasing current causes an irresistible convulsive contraction of the muscles of the arm 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 constant current should be 50-70 mA. A person cannot open his hand on his own and free himself from the influence of current.
Fibrillation current causes fibrillation (fluttering) of the heart muscle. These are fast, chaotic and multi-temporal contractions of cardiac muscle fibers (fibrils). As a result, the heart loses its ability to pump blood, the body’s circulatory and respiratory processes cease, and death occurs. When exposed to alternating current of industrial frequency, the threshold fibrillation current is 100 mA (with a duration of 0.5 seconds), and for direct current - 300 mA with 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 current passage through the human body has a significant influence on the outcome of the injury. Prolonged exposure to 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, since this increases the local heating of the skin, which leads to the expansion of its vessels, to an increased supply of blood to this area and an increase in sweating.
The path of electric current through the human body. The path of current through the human body plays a significant role in the outcome of the injury, 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 skin resistance in various parts of the body. Possible current loops: arm-arm, arm-legs and leg-leg. The most dangerous loops are head-arms and head-legs, because the respiratory organs and 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 and non-releasing currents for alternating and direct currents. Cases of injury 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. For more high voltages D.C. more dangerous than variable.
For alternating current, its frequency also plays a role. As the frequency of alternating current increases, the impedance of the body decreases, which leads to an increase in the current passing through a person, therefore, the risk of injury increases. The greatest danger is represented by current with a frequency of 50 to 1000 Hz; with a further increase in frequency, the danger of injury decreases and completely disappears at a frequency of 45-50 kHz. These currents remain a risk of burns.
Individual properties of a person. It has been established that physically healthy and strong people can more easily tolerate electric shocks. Persons suffering from diseases of the skin, cardiovascular system, internal secretion organs, lungs, and nervous diseases are characterized by increased susceptibility to electric current. Safety rules for the operation of electrical installations provide for the selection of personnel to service existing electrical installations based on health conditions. For this purpose, a medical examination of persons is carried out upon entry to work and periodically once every two years in accordance with the list of diseases and disorders that prevent access to servicing existing electrical installations.
Environmental conditions. 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. High temperature and humidity of the surrounding air reduce 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 exposure to current on a person, the “Rules for the Construction of Electrical Installations” 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 electric shock to people 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 insulation and live parts of electrical equipment;
- · simultaneous implementation of two or more conditions of increased danger. Examples of such premises include baths, showers, underground storage facilities, etc.
- 2. Premises with an increased risk of electric shock to people are characterized by the presence 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 human touch to the metal structures of buildings and mechanisms connected to the ground, on the one hand, and to the metal casings of electrical equipment, on the other. Examples of such premises include drilling rigs, oil pumping stations, mechanical processing shops, warehouses unheated premises and 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 bureaus, plant management, office premises and others.
Protecting people 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 production, transmission, distribution electrical energy.
Electric shock to a person is possible only when an electrical circuit is closed through his body or, in other words, when a person touches the network at at least two points.
TOUCH VOLTAGE (Upr) is the potential difference between two points of an electrical circuit that are simultaneously touched by a person. It happens:
- · with two-phase connection to the network;
- · during single-phase connection to the network (in contact with live parts of equipment - terminals, buses, etc.);
- · in contact with non-current-carrying parts of equipment that accidentally become energized due to broken wire insulation;
- · when step stress occurs.
The current (J) flowing through the human body is equal to
where Upr - touch voltage; Rch is the resistance of the human body.
The current can be reduced either by reducing the touch voltage (using low voltages) or by increasing human resistance (using PPE).
When a person is connected two-phase to the network, the touch voltage will be equal to the line voltage. If a person touches an electrically damaged installation that is grounded, then the touch voltage will be lower than the voltage of this installation, since any grounding device reduces the potential of the electrical installation body.
Step voltage is the potential difference between two points on the surface of the earth on which a person stands at the same time. A potential difference occurs when a bare wire falls to the ground or when approaching a 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 ground; r is the radius of the conductor; a is the estimated step length equal to 0.8 m; x is the distance from the center of the conductor to the nearest human leg.
The higher the potential of the wire touching the ground and the shorter the distance (x), the higher the step voltage value. The tension of the step 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 Interindustry Rules for the Operation of Electrical Installations (2001).
Technical means of protection against electric shock are divided into collective and individual.
Basic collective methods and means of electrical protection:
* insulation of conductive parts (wires) and its
continuous monitoring;
- * installation of fencing 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 refer to protection against touching live parts of installations.
Insulation of conductive parts is one of the main electrical safety measures. According to the PUE, the insulation resistance of conductive parts of electrical installations relative to the ground must be at least 0.5 MOhm (1 MOhm = 106 Ohm.)
There are working and double insulation.
Working is called insulation that provides normal work electrical installation and protection of personnel from electric shock.
Double insulation, consisting of working and additional insulation, is used in cases where it is necessary to ensure increased electrical safety of equipment (for example, hand power tools, household electrical appliances, etc.).
There are basic and additional insulating agents. Basic insulating electrical protective equipment can withstand the operating voltage of electrical installations for a long time, so they are allowed to touch live parts under voltage. In installations up to 1000 V, these are dielectric gloves, tools with insulated handles, and 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 agents with which they must be used. In installations up to 1000 V - dielectric boots, dielectric rubber mats, insulating stands.
Installation of fencing 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 touch. Structurally, fences are made of solid metal sheets or metal mesh.
Warning signals and lockouts. To warn of the danger of electric shock, various sound, light and color alarms are used. In addition, the designs of electrical installations provide interlocks - automatic devices that block the path to the danger zone. Locks can be mechanical (stoppers, latches, shaped cutouts), electrical or electromagnetic.
To inform personnel about the danger, warning posters are used, which, according to their purpose, are divided into warning, prohibiting, permitting and reminding. Parts of equipment that pose a danger to people are painted in signal colors. They are marked with a safety sign in accordance with GOST 12.4.026 “Signal colors and safety signs.” Buttons and levers are colored red emergency shutdown electrical installations.
Application of low voltages. To reduce the risk of electric shock to people working with portable power tool and lighting lamps in particularly hazardous areas, use a low voltage not exceeding 42 V. In some cases, for example, when working in mines, a voltage of 12 V is used to power hand-held portable lamps. Low voltage sources are transformers, batteries, batteries of galvanic cells and etc.
When current shorts to metal parts of equipment (short circuit to the body), voltages appear on them that are sufficient to injure people. In this case, protection against electric shock can be achieved in three ways: protective grounding, grounding and protective shutdown. They protect a person from voltage that appears on the housing 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 live if the insulation of the electrical installation is damaged. Protective grounding is installed 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 touch voltage (Vpr), which is determined by the expression:
Vpr = Vз - Vx,
where Vз is the total voltage on the electrical installation body, V; Vx - potential of the ground or floor surface, V.
The operating principle of protective grounding is to reduce touch voltages caused by a short circuit to the housing to safe values.
All metal parts of electrical installations and equipment, for example, housings, are subjected to protective grounding electric machines, transformers, lamps, frames distribution boards, metal pipes and shells of electrical wiring, as well as metal housings of portable electrical receivers.
Structurally, the grounding device consists of metal electrodes (angle and metal pipes at least 2.5 m long) connected to each other by a metal strip, which is applied to 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 ground loop resistance.
Depending on the relative position of the grounding conductors and the equipment being grounded, remote and loop grounding devices are distinguished. The first of them are characterized by the fact that the grounding conductors are located 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 short distance from each other (several meters), provides a better degree of protection than the previous one.
Grounding electrodes can be 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, reinforcement of reinforced concrete structures, lead cable sheaths, etc. Artificial grounding conductors are made from steel pipes, corners, rods 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 intended to protect personnel from electric shock in four-wire networks with a solidly grounded neutral up to 1000 V. Typically these networks are 220/127, 380/220 and 660/380 V.
Grounding is a deliberate connection to the neutral conductor of metal parts of equipment that may be energized. The operating principle of grounding is to transform a short circuit to the housing into a single-phase short circuit. The purpose of this is to generate a large current capable of triggering the protection and thereby automatically disconnecting the damaged installation from the supply network. Such protection can be: fuses, magnetic starters and circuit breakers.
The response time of the protection elements depends on the current strength. Thus, for fuses and thermal circuit breakers, the fuse response 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 voltages up to 1000 V, by automatically shutting off all phases of the emergency section of the network within a time acceptable under human safety conditions.
The main characteristic of this system is its speed; it should not exceed 0.2 s. The principle of protection is based on limiting the time of dangerous current flowing 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 short-circuited to a grounded or neutralized housing of an electrical installation, housing voltage appears on it. If it exceeds a predetermined maximum permissible voltage, a protective shutdown device is triggered. The operation of the protective shutdown circuit is presented in. It is recommended to use protective shutdown 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 disconnect electrical equipment remote from the power source, as an addition to grounding;
- * in electrified tools as a supplement to protective grounding or grounding;
- * in rocky and frozen soils if it is impossible to perform the necessary grounding.
Organizational measures ensuring safe operation electrical installations. These include registration of the relevant work in an order or order, permission to work, supervision of work, strict adherence to the work and rest regime, 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, defining the content, place, start and end time of the 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 performance of work, but indicating the content of the work, place, time and persons entrusted with its implementation.
All work on conductive parts of electrical installations under voltage and with voltage relief is carried out separately, 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 by order.
Organizational measures also include training personnel in the correct work techniques with assigning appropriate qualification groups to employees servicing electrical installations.
Providing first aid to a person struck by an electric current. First aid to a person struck by electricity consists of two stages: freeing the victim from the effects of electric current and providing him with first aid.
If a person has touched a conductive part of an electrical installation and cannot independently free himself from the influence of the current, then those present must help him. To do this, quickly disconnect the electrical wiring using a switch, 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 that without using necessary measures As a precaution, you should not touch a person who is in the current circuit, as you yourself may become energized.
If the victim is exposed to a voltage of 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 they are dry. The hands of the person providing assistance should be protected with dielectric gloves; rubber shoes should be put on their feet or stand on an insulating stand (dry board).
If the above measures do not produce results, it is permissible to cut the wire with an ax with a dry wooden handle or cut it with another tool with insulated handles.
At voltages exceeding 1000 V, those providing assistance must work in dielectric gloves and shoes and pull the victim away from the wire with special tools designed for this voltage (bar or pliers). It is also recommended to short-circuit all power line wires by throwing a wire connected to the ground over them.
After freeing the victim from the effects of electric current, he is provided with pre-medical medical care. If the person who has received an electrical injury is conscious, he must be ensured complete rest until a doctor arrives or be urgently taken to a medical facility.
If a person has lost consciousness, but breathing and heart function are preserved, the victim is laid on a soft mat, the belt and clothes are unfastened, thereby ensuring the flow of fresh air. Then they let you smell it ammonia, |rub and warm the body. If breathing is rare, convulsive, or worsening, the victim is given artificial respiration. In the absence of signs of life, artificial respiration is combined with external cardiac massage.
Questions for self-control
What effect does electric current have on the human body?
What are electrical injuries?
What are the causes of electrical injuries?
What factors determine the outcome of an electric shock?
Describe the permissible levels of electric shock?
List the main cases of connecting a person to an electrical network.
What is step voltage?
List the main methods and means of electrical protection and describe them?
Classification of 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 grounding and what is the principle of ensuring electrical safety with its help?
What is a protective shutdown and what are the principles of its operation?
Name individual means protection against electric shock?
Irina Lagodovets
Summary of a lesson on life safety in a school preparatory group " Magic electricity»
Summary of a lesson on life safety in a preparatory school group
« MAGICAL ELECTRICITY»
Target: developing safe behavior skills when handling electrical appliances.
Educational:
summarize children's knowledge about electrical appliances, about their purpose in everyday life;
introduce concepts « electricity» , « electricity» ;
introduce the rules for safe handling electrical appliances.
Developmental:
develop the ability to work with models;
develop the desire for search and cognitive activity;
develop mental activity, curiosity, and the ability to draw conclusions.
Educational:
cultivate interest in understanding the world around us;
evoke the joy of discovery gained from experience.
Equipment: slides, pictures with images electrical appliances, wires
Progress of the lesson
1. INTRODUCTION
Hello guys. Today we will talk about electricity, about safety in the house, let's play Interesting games, let's find out how electricity appears in our homes, and we will conduct interesting experiments.
Now I will read you a poem. Listen very carefully and guess what kind of helpers it talks about m:
We love our home very much,
Both cozy and dear.
But not everyone could
Redo a lot of things.
We need to clean the house,
Cook, wash,
And also iron the clothes...
How to cope with all the work!
And it’s wonderful that now
We have helpers.
They make our work easier
They save our time.
What helpers are mentioned in the poem?
How can you call these devices in one word? (electrical appliances) .
2. DIDACTIC GAME "COLLECT PICTURES"
Let's play a game "Collect a picture". There are cut up pictures on your tables. Collect them and name what happened.
You named all the devices correctly, and now I suggest you play the game "What is it for":
I call electrical appliance, and you must say what actions it performs (iron, hair dryer, microwave, refrigerator, kettle, electric stove, telephone, vacuum cleaner, mixer, fan).
Do you see how much electrical appliances surround us. They are our best helpers. All of them make our life convenient and varied. Without them it would be difficult for a person. All these devices operate from electricity.
3. DIDACTIC GAME "WHAT IS, WHAT WAS"
Imagine that we found ourselves in a time when people still knew nothing about electricity, and therefore about electrical appliances he didn't know and didn't think. But that man cooked his own food, washed his clothes, and cleaned his home.
Let's play a game "What is, what was". Look at the pictures, think and name which ones are modern electrical appliances replaced old things.
This is a trough. What do you think they did in it? Which electric the device has replaced it now (slide show)
Washing machine - trough;
Vacuum cleaner - broom;
Mixer - whisk;
Iron – ironing stick, charcoal iron;
Sewing machine - needle;
Electric lamp - candle;
Tape recorder - accordion, balalaika.
Well done, you completed the task. Now you know how much household appliances perfected by man, thanks to electricity.
What do you think is needed for everything? electrical appliances started working? (Children's answers).
Absolutely right. All electrical appliances run on current. But, before I tell you where the current comes from, let’s warm up a little.
PHYSMINUTE
Imagine that you are small particles of current running through wires (children run in a circle after each other):
The current runs through the wires (they run in a circle,
The light brings into our apartment (flashlights up)
For the devices to work
Refrigerator, monitors
Coffee grinders, vacuum cleaner
The current brought energy...
4. TEACHER'S STORY
“WHERE DOES IT COME FROM? ELECTRICITY»
Have you rested? Now let's continue our conversation about electricity. Please listen carefully to my story.
Electric current is generated at large powerful power plants. To obtain electricity, at such stations the power of water, heat, sun, and wind is used. Then, electric Current flows through wires hidden deep underground or very high above the ground and comes into our homes, ending up in switches and sockets.
Electric The current makes a long journey through the streets and alleys, along wires and is somewhat similar to a river, only water flows in the river, and small, very small particles flow through the wires.
This wire is a track. On top she is dressed in a rubber shirt, and under it is a bundle of thin copper wires, through which current flows into houses, hospitals, schools, kindergartens.
Did you listen carefully to my story? Look at Pictures: This power station. This power station works from water - it is water, this one works from heat, which means it is thermal. This power station Powered by the sun - what does it mean? (Solar). And this one works from the power of the wind - it is wind-powered.
Who remembers from my story what is the name of the path along which the current flows? Where do the wires go? (Pictures and wires).
5. KNOW THE RULES
(Scheme)
So, let's continue our conversation about electricity. Electric current is very dangerous, it can even kill, so you need to follow safety rules when working with electrical appliances. You need to communicate with them correctly. Today I will introduce you to the rules that will help you avoid trouble.
Look carefully at this picture, think and tell me what this means?
1. DO NOT put it in electrical foreign objects, especially metal ones, into the socket! Because the current, like a bridge, can move to you, seriously injure you and even kill you.
2. DO NOT touch bare wires with your hands! Flows through a bare wire not protected by insulation. electricity, the blow of which can be fatal.
3. DO NOT touch the switched on electrical appliances with wet hands! Available swipe current, since water is a conductor electric current.
4. DO NOT leave it on electrical appliances unattended! Included electrical appliances may cause a fire. When leaving home, always check that the lights are off, the TV, tape recorder are turned off, electric heater, iron, stove, etc.
5. DO NOT overload with work electrical appliances! A short circuit may occur, leading to a fire.
6. DO NOT use faulty sockets, electrical appliances! This can also lead to a fire.
7. DO NOT turn on electrical appliances without the permission of adults and in their absence!
If you follow these simple rules, then electricity will always be your friend.
You and I have already talked a lot about electricity. Did you remember that electricity could it be very dangerous? (Children's answers). And what do you think? Eat electricity is safe, which you can play with? (Children's answers).
But no! Electricity can be harmless. It lives on its own, and if you catch it, you can play with it in an interesting way. I invite you to conduct some educational experiments!
6. EXPERIMENTS WITH STATIC ELECTRICITY
Ball hanging on the wall
Guys, what is this? (Balloon). Right. What do you think is in the ball? electricity? (Children's answers). And now I’ll prove to you that there is something safe that lives in a balloon. electricity. And you can even play with it.
To do this, you need to rub the ball on your hair and apply it to the wall with the side you rubbed. He became electric and therefore stuck to the wall.
Well, it's in a balloon electricity? (Children's answers).
Experience with a plastic comb
Hair become electrified, become naughty.
Conclusion: lives in hair too electricity.
Magic flowers
A piece wool fabric rub a plastic stick, slowly bring it to the flower from paper napkin and pick it up. The flowers will also rise.
Battery experience
The flashlight does not turn on without a battery, but when you put the battery in – plus – to plus, minus – to minus – it shines.
Conclusion: there is something harmless in the battery electricity.
You guys are great, you learned how to make objects magical. Now you know that in such simple objects as a comb, balloon, the napkin lives electricity, but what is it? (Safe).
So, guys, today we talked a lot about electricity and electrical appliances.
About which electrical appliances we spoke to you on class?
Who remembers how modern electrical appliances replaced old household items? The washing machine replaced which item? What about a vacuum cleaner?
Still today on we learned in class, What electricity there is something dangerous and something safe. And where is dangerous found? electricity?
Where can we find something safe? electricity?
What rules should we follow to avoid trouble at work? electrical appliances?
Introduction
1. The effect of electric current on the human body
2. Factors that determine the outcome of electric shock
3. Maximum permissible voltage and current values
Conclusion
Literature
INTRODUCTION
This work examined the principles and means electrical protection. In particular, zeroing. Also included in the work were questions such as:
The effects of electric current on the human body;
Factors that determine the outcome of electrical lesions. electric shock;
Acceptable levels touch voltages and currents;
Scheme, purpose, principle of operation and scope of application of zeroing;
Solving the problem on the topic “Zeroing”.
1. ACTION EL. CURRENT ON THE HUMAN BODY
When operating and repairing electrical equipment and networks, a person may be exposed to an electric field or in direct contact with live electrical wiring. As a result of the passage of current through a person, a disruption of his vital functions may occur.
The danger of electric shock is aggravated by the fact that, firstly, the current has no external signs and, as a rule, a person without special devices cannot detect the danger threatening him in advance; secondly, the impact of current on a person in most cases leads to serious disruptions of the most important vital systems, such as the central nervous, cardiovascular and respiratory systems, which increases the severity of the damage; thirdly, alternating current can cause intense muscle cramps, leading to a non-releasing effect in which a person cannot independently free himself from the influence of the current; fourthly, exposure to current causes a sharp withdrawal reaction in a person, and in some cases loss of consciousness, which, when working at height, can lead to injury as a result of a fall.
Electric current passing through the human body can have biological, thermal, mechanical and chemical action. The biological effect is the ability of an electric current to irritate and excite living tissues of the body, the thermal effect is the ability to cause burns to the body, the mechanical effect is to lead to tissue rupture, and the chemical effect is to lead to electrolysis of blood.
The effect of electric current on the human body can cause electrical injury. An electrical injury is an injury caused by exposure to an electric current or arc. Conventionally, electrical injuries are divided into local and general. With local electrical injuries, local damage to the body occurs, expressed in the appearance of electrical burns, electrical signs, metallization of the skin, mechanical damage and electroophthalmia (inflammation of the outer membranes of the eyes). General electrical injuries, or electrical shocks, lead to damage to the entire body, expressed in disruption or complete cessation of the activity of the most vital organs and systems - lungs (breathing), heart (circulation).
The nature of the effect of electric current on a person and the severity of the injury to the victim depends on many factors.
The danger of exposure to electric current on a person can be assessed by the body’s responses. As the current increases, three qualitatively different responses clearly appear. This is first of all a sensation, a more convulsive contraction of the muscles (non-release for alternating current and the painful effect of constant) and, finally, cardiac fibrillation. Electric currents that cause a corresponding response are divided into palpable, non-releasing and fibrillation.
2. FACTORS DETERMINING THE OUTCOME OF ELECTRIC SHOCK
Factors influencing the outcome of electric shock include:
1. Current value.
2. Voltage value.
3. Action time.
4. Type and frequency of current.
5. Closing path.
6. Human resistance.
7. Environment.
8. Attention factor.
2.1. Current value
According to the current value, currents are divided into:
Insensible (0.6 – 1.6 mA);
Sensible (3mA);
Release (6mA);
Non-releasing (10-15mA);
Asphyxiating (25-50mA);
Fibrillation (100-200mA);
Thermal effects (5A and above).
2.2. Voltage value and 2.3. Time of action
According to GOST 12.1.038-82 SSBT “Maximum permissible values of voltages and currents. Electrical safety". Factors of voltage magnitude and time of exposure to electric current are given in table. 1.
Table 1
With short-term exposure (0.1-0.5 s), a current of about 100 mA does not cause cardiac fibrillation. If you increase the duration of exposure to 1 s, then the same current can lead to death. With a decrease in the duration of exposure, the value of currents permissible for humans increases significantly. When changing the exposure time from 1 to 0.1 s permissible current increases by 16 times.
In addition, reducing the duration of exposure to electric current reduces the risk of injury to a person based on certain features of the heart. The duration of one period of the cardiac cycle (Fig. 2.1.) is 0075-0.85 s.
In each cardiac cycle, there is a period of systole, when the ventricles of the heart contract (QRS peak) and push blood into the arterial vessels.
Phase T corresponds to the end of ventricular contraction and they enter a relaxed state. During diastole, the ventricles fill with blood. Phase P corresponds to atrial contraction. It has been established that the heart is most sensitive to the effects of electric current during the T phase of the cardiac cycle. In order for cardiac fibrillation to occur, the time of exposure to current must coincide with the T phase, the duration of which is 0.15-0.2 s. With a reduction in the duration of exposure to electric current, the likelihood of such a coincidence becomes less, and therefore, the danger of heart fibrillation decreases. If the time of passage of the current through a person does not coincide with the T phase, currents significantly exceeding the threshold values will not cause cardiac fibrillation.
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