Types of electric shock to a person presentation. What is the danger of electric current. OBZh lesson

2.8. Electricity. Electric shock hazard analysis1
2.8. Electricity.
Electric shock hazard analysis
Electrical network diagrams
ZNT
NT Ul
0
INT
Uф
0
R0 \u003d 2-8 Ohm
U l 3 Uph
FROM
R and
ZNT - a network with a grounded neutral point of the transformer;
Anv
INT - network with an isolated neutral point (NT);
(0 - 0) - zero protective conductor; R0 - working grounding of NT;
Ri - insulation resistance of the phase relative to earth; С - capacity;
Ul - line voltage (380V); Uph - phase voltage (220V).

Dangerous situations of electric shock

2
Dangerous situations of electric shock
1. Accidental two-phase or single-phase touching
live parts.
2. Approaching a person at a dangerous distance to the tires of high
voltage (according to the standards, the minimum distance is 0.7 m.)
3. Touching non-conductive metal parts
equipment that may be energized due to
damage to insulation or erroneous actions of personnel.
4. Getting under a step voltage when moving a person
along the area of \u200b\u200bcurrent spreading from a wire that fell to the ground or
short circuits of live parts to ground.
Anv

Two-phase contact with live parts

3
Two-phase touch to
live parts
The most dangerous case is touching two
phase wires (a) and to the phase and neutral wire (b).
and)
b)
Uл
A Current Ich passing
In through a person, and
contact voltage
changes Upr (V) at
resistance
Uф
Human Rh (Ohm):
Hand-to-hand current path
and)
I h U l / Rh, U pr I h Rh U l 380 V
b) I h U f / Rh, U pr I h Rh U f 220 V
The touch voltage is the potential difference between two
points of the chain that the person touches the surface of the skin.
Anv

6
Figure: 42 Hazardous situations of electric shock
in the household sphere.
2.16. The impact of current on a person
Anv

The impact of current on a person

1
The impact of current on a person
Electrical injury
1. Burns - current and arc.
2. Electrical signs are current marks occurring at a place
current input or current path (streaks and dark spots)
3. Skin metallization is the penetration of molten splashes
metal from the arc into the skin.
4. Mechanical damage from convulsive muscle contractions.
5. Electrophthalmia is damage to the cornea of \u200b\u200bthe eyes from
electric arc (for example, when welding).
Anv

Electric shock

2
Electric shock
When a person is connected to an electrical network,
closed "chain of defeat" and the current passing through a person
Ich (A), will determine the degree of danger.
Ih
U pr
Rh
,
where Upr - contact voltage, V;
Rh - resistance of the human body, Ohm.
Electric shocks have different consequences:
1. A person can independently break away from the guide,
vital activity is preserved, but then there may be
Anv
adverse deviations in health.
2. A person cannot independently tear himself away from the guide and
for a long time is under the influence of current. As a result
this is possible shock, paralysis of the respiratory system,
cardiac fibrillation (irregular contraction of fibers
heart muscle, which is often fatal).

Factors influencing the risk of electric shock

3
Factors influencing the hazard
electric shock
1. The strength of the current, time and path of its passage through a person
(the most dangerous paths are “hand-hand”, “hand-leg”, “left arm-legs”).
2. The nature and frequency of the current (alternating current is considered more dangerous,
than constant, and with increasing frequency the danger of current
decreases.)
3. Type of electrical network (usually networks with ZNT are more dangerous than
networks with INT).
4. Resistance of the human body, which lies in the range of 0.3 -100
kOhm, but usually it is 2000 - 10000 Ohm, and the resistance
internal human organs is equal to 300 - 500 ohms.
When calculating, the human resistance Rch is taken as 1000 Ohm.
Rh depends on: skin condition (dry, wet, damaged);
health conditions, psychophysiological
Anv
features, the factor of "attention".

Current thresholds. Limiting current

4
Current thresholds.
Limiting current
For alternating current with a frequency of 50 Hz, thresholds are set:
Sensible current (1 - 3 mA)
Non-releasing current (10 - 15 mA).
The current causing paralysis of the respiratory muscles (60 - 80mA).
Fibrillation (lethal) current (100 mA at t\u003e 0.5 s).
Safe for humans, the current is 0.3 mA.
Limiting
current strength at exposure time
1 second is 50 mA, and at a time of 3 s. - 6 mA.
2.17. Electrical safety equipment
Anv

Electrical safety equipment

1
Electrical safety equipment
Electrical safety equipment is divided into technical and protective.

1. Selection of electrical equipment of the corresponding design in
dependencies
from
conditions
exploitation
(protected,
splash-proof, explosion-proof, etc.)
2. Insulation of live parts, which is the first and
the main stage of protection. Insulation resistance
for individual sections of the network is 0.3 - 1 MOhm. Isolation
divided into working, double and reinforced.
3. Protection against accidental contact with live parts:
- fencing, blocking;
- location of live parts at an inaccessible height;
- protective shutdown that reacts to the touch of a person
century to live parts.

Electrical safety equipment (continued)

2
Technical means of electrical safety
(continued)
4. Application of low voltages (12 - 42 V) in especially hazardous
premises.
5. Means for reducing the capacitive current: switching on the inductive
coils between neutral point and ground, separation
extended networks into separate sections with a lower capacity.
6. Means of protection against phase breakdown on the equipment case:
Protective earth
Zeroing
0
Safety shutdown
Anv

Protective earth

3
Protective earth
Protective earth is the connection between the equipment chassis and
ground through a small resistance (4 - 10 ohms). When
phase breakdown to the case, the potentials of the equipment are compared.
and the foundations of phon, and Upr and the current through a person become less.
It is used mainly in networks with INT up to 1000 V.
U pr about main
Ih
Iз
Rz
R and
In parallel branches, currents are inversely proportional to resistances.
Rz
Ih I s
,
R
where R is the total resistance of a person, shoes
and gender, Ohm.
Anv

Zeroing

4
Zeroing
Zeroing is the connection of the equipment body with zero
protective conductor. When a phase breaks down to the case,
high short-circuit current, automatic
switches (AB) or fuse links burn out
(OL) and the installation is shut down. It is used in networks with ZNT up to 1000V
Trigger condition
protection:
0
Ikz
AB (Pr)
0
I kz I nom K,
where Inom - rated operating current
protection; K - current multiplicity factor.
Anv

Residual current device (RCD)

5
Residual current device (RCD)
RCD is a fast-acting protection that reacts to short circuit
phases to the body, to the ground, to the touch of a person.
RCD characteristics: setting and response time (0.05 - 0.2 s.).
It is used as an independent means of protection and in combination with
grounding or grounding.
RCD circuit responsive to change
frame voltage to ground
TO
PH
In case of phase breakdown to the case
voltage relay is activated
(PH) adjusted to a specific setpoint and setting
switched off by a contactor (K).
Anv

Electrical protective equipment

6
Electrical protective equipment
They are divided into main ones (they allow you to work on live parts)
and additional (enhance the effect of the main).
a - insulating
barbell;
b - insulating
ticks;
c - measuring
ticks;
d - voltage meter\u003e 1000 V;
d - the same< 1000 В;
e - dielectric
gloves, galoshes;
w-rugs, stands
h - portable grounding Fig. 43
nie.
Anv

First aid for victims of electric shock

1
First aid to victims
from electric current

The main thing is speed
actions, since than
more time man
is energized, the
less chance of it
the rescue.
First of all
must be disabled
installation with
knife switch,
plug connector
or unscrew the plug.
Figure: 44
Anv

Freeing the victim from the current (continued 1)

2
Release of the victim from the current
(continued 1)
If you cannot turn off the power supply, the actions
for the salvation of a person should be selected depending on
voltages: conventional networks (up to 1000 V) or high-voltage
networks (more than 1000 V).
Networks up to 1000 V
To separate the victim from the wire, you can
use clothes, rope, stick, board. These items
must be absolutely dry. Should not touch
the victim's feet, as the shoes may be damp. For
use rubber gloves to isolate the hands of the rescuer,
scarf, sleeve, dry cloth. You can stand on a dry board
or bedding. To interrupt the current, you must slip
under the injured dry board, cut the wire
Anv
ax with a dry wooden handle.

Freeing the victim from the current (continued 2)

3
Release of the victim from the current
(continued 2)
Figure: 45
Anv

Freeing the victim from the current (continued 3)

4
Release of the victim from the current
(continued 3)
Networks over 1000 V
In such networks, to separate the victim from the current
it is imperative to use electrical protection
means: insulating boots, dielectric gloves, and
it is necessary to act with an insulating rod.
Determination of the condition of the victim
1. Immediately lay the victim on his back.
2. Unbutton tight clothing.
3. Check the presence of breathing by the movement of the chest.
4. Check for a pulse.
5. Check the condition of the pupil (narrow or wide).
6. Provide rest to the victim until the arrival of the doctor.
In case of infrequent breathing or no signs of life
need to do artificial respiration and indirect massage
hearts.
2.19. Combustion processes; fire hazards

Slide 2

How does electric current affect a person

The fact of the effect of electric current on a person was established in the last quarter of the 18th century. The danger of this action was first established by the inventor of the electrochemical high-voltage voltage source V.V. Petrov.

Slide 3

Electric current, electrical injuries and electrical injuries

Electric shock is an injury caused by an electric current or electric arc.

Slide 4

Electrical traumatism is characterized by the following features: a protective reaction of the body appears only after a person gets under voltage, that is, when an electric current is already flowing through his body; electric current acts not only in the places of contact with the human body and on the path of passage through the body, but also causes a reflex action, manifested in the disruption of the normal activity of the cardiovascular and nervous system, breathing, etc.

Slide 5

A person can get an electrical injury both by direct contact with live parts, and by being hit by a touch or step voltage through an electric arc.

Slide 6

Electric injury in comparison with other types of industrial injuries is a small percentage, however, in the number of injuries with severe, and especially fatal, it takes one of the first places. Leather metallization

Slide 7

The largest number of electrical injuries (60-70%) occurs when working on electrical installations with voltage up to 1000 V.

Slide 8

Causes of electric shock to a person

The causes of electric shock to a person are as follows: touching non-insulated live parts; to metal parts of the equipment that are energized due to insulation damage; to non-metallic objects that are energized; shock voltage step and through the arc.

Slide 9

Types of electric shock to a person

The electric current flowing through the human body affects it thermally, electrolytically and biologically.

Slide 10

The thermal effect is characterized by tissue heating, up to burns; electrolytic - by the decomposition of organic fluids, including blood; the biological effect of electric current is manifested in the violation of bioelectric processes and is accompanied by irritation and excitation of living tissues and muscle contraction.

Slide 11

Electrical injuries are local lesions of tissues and organs: electrical burns, electrical signs and electrometallization of the skin.

Slide 12

Electrical burns occur as a result of heating human tissues by an electric current of more than 1 A flowing through it. Burns can be superficial, when the skin is affected, and internal ones, when deep-lying body tissues are damaged. According to the conditions of occurrence, contact, arc and mixed burns are distinguished.

Slide 13

Electrical signs are spots of gray or pale yellow in the form of a callus on the skin surface at the point of contact with live parts. Electrical signs are usually painless and subside over time.

Slide 14

Electrometallization of the skin is the impregnation of the surface of the skin with metal particles when it is sprayed or evaporated under the influence of an electric current.

Slide 15

Electric shock is the excitation of living tissues with an electric current, accompanied by an involuntary convulsive muscle contraction.

Slide 16

Clinical, or "imaginary", death is a transitional state from life to death. In a state of clinical death, cardiac activity stops and breathing stops. The duration of clinical death is 6 ... 8 minutes. After this time, the cells of the cerebral cortex die, life fades away and irreversible biological death occurs.

Slide 17

Electric shock is a severe neuroreflex reaction of the body to irritation with an electric current. In shock, deep disorders of breathing, blood circulation, nervous system and other body systems occur.

Slide 18

What determines the degree of action of electric current on the human body

The outcome of the lesion also depends on the duration of the current flowing through the person. With the increase in the duration of a person's stay under stress, this danger increases.

Slide 19

The individual characteristics of the human body significantly affect the outcome of injury in electrical injuries. For example, a non-releasing current for some people may be a threshold perceptible for others. The nature of the action of the current of the same strength depends on the mass of a person and his physical development. It was found that for women the threshold current values \u200b\u200bare approximately 1.5 times lower than for men.

Slide 1

Slide 2

How an electric current acts on a person The fact that an electric current acts on a person was established in the last quarter of the 18th century. The danger of this action was first established by the inventor of the electrochemical high-voltage voltage source V.V. Petrov.

Slide 3

Electric current, electrical injury and electrical injury Electric shock is an injury caused by the action of an electric current or electric arc.

Slide 4

Slide 5

A person can get an electrical injury both by direct contact with live parts, and by being hit by a touch or step voltage through an electric arc.

Slide 6

Slide 7

The largest number of electrical injuries (60-70%) occurs when working on electrical installations with voltage up to 1000 V.

Slide 8

Causes of electric shock to a person The reasons for electric shock to a person are as follows: touching non-insulated live parts; to metal parts of the equipment that are energized due to insulation damage; to non-metallic objects that are energized; shock voltage step and through the arc.

Slide 9

Types of electric shock to a person The electric current flowing through the human body affects it thermally, electrolytically and biologically.

Slide 10

Slide 11

Electrical injuries are local lesions of tissues and organs: electrical burns, electrical signs and electrometallization of the skin.

Slide 12

Slide 13

Electrical signs are spots of gray or pale yellow in the form of calluses on the surface of the skin at the point of contact with live parts. Electrical signs are usually painless and subside over time.

Slide 14

Electrometallization of the skin is the impregnation of the surface of the skin with metal particles when it is sprayed or evaporated under the influence of an electric current.

Slide 15

Electric shock is the excitation of living tissues with an electric current, accompanied by an involuntary convulsive muscle contraction.

Slide 16

Slide 17

Slide 18

What determines the degree of action of the electric current on the human body The outcome of the defeat also depends on the duration of the current flow through the person. With the increase in the duration of a person's stay under stress, this danger increases.

Slide 19

Back forward

Attention! The slide preview is used for informational purposes only and may not represent all the presentation options. If you are interested in this work, please download the full version.

Lesson type: knowledge system building lesson

Lesson type: integrated - connection of physics with OBZH.

The purpose of the lesson:

In an unconventional, entertaining way, repeat and update the studied material.
Teach to apply knowledge in a new situation.
Form an idea of \u200b\u200bthe danger of electric current.
Form teamwork skills in combination with students' independent activities.
Develop interest, the desire to penetrate into the essence of phenomena, a vision of the significance of the material studied.

Lesson Objectives:

Educational: to repeat and consolidate the basic laws, to form the skill of solving qualitative and experimental problems.
Developing: development of cognitive motivation, logical thinking, development of the regulatory sphere based on self-control, mutual control.
Educational: education of personal qualities: activity, enthusiasm, quick wit.

Planned results: students will learn to apply the knowledge gained in practice, process the information received, draw conclusions as a result of joint work.

Resources:textbook, notebook, current source, ammeter, voltmeter, light bulb, wires, key.

Equipment: computer, smart board, blackboard.

Organization of space: frontal work, group work, work in pairs

During the classes

I. Organizational moment. Motivation for learning activities.

It will be interesting today
Not boring at all, not bland at all!
What is your source of interest?
Important topic: "Electric current"

II. Knowledge update. Demonstration of slides.

"Lightning", "LEP"

- Tell me, guys, what unites these slides?

- Electricity

III. Statement of the topic of the lesson.

Electricity is everywhere
Both on land and in water.
It even happens in space!
And the atmosphere "rumbles"!
Everyone knows about the benefits of electricity
But the danger is forgotten!

- Guys, formulate the topic of today's lesson

- "Useful and dangerous electric current"

- Who can formulate the main goal of our lesson?

- Find out what the benefits and dangers of electric current are.

IV. Repetitionse.

1. What is electric current?

- Electric current is the directed movement of charged particles.

2. Conditions for the existence of email. current in the circuit?

- The presence of a current source, the presence of charged particles.

3. Where is the email generated? current?

- At thermal power plants, hydroelectric power plants, nuclear power plants, unconventional power plants

4. Basic laws of electric current?

- Ohm's law, Joule-Lenz's law, laws of consistent and parallel connection conductors.

5. What devices measure current and voltage?

- Ammeter, voltmeter

6. Where is electrical energy used?

- At home, in transport, in industry

7. What device allows us to determine the amount of energy consumed?

- Electric meter

V. Checking homework.

- Guys, now let's check your homework.

1. How did you determine the consumption and cost of electricity in your apartment using the meter for 5 days?

The teacher checks the written homework. Together with the students, he discusses who is saving energy.

2. Guys, you had a task: to find ways to save energy in additional literature. Let's discuss and reflect together.

Vi. Application of the acquired knowledge in a new situation (presentation: "We save electricity").

Now I will show slides with the advice of a young physicist, and we will discuss these tips and draw up a memo on saving electrical energy.

Young Physicist Tips
1. When leaving, turn off the light. Here's a saving secret!	1. Everyone understands this.
2. Two-tariff meter Put it in the apartment! To save energy Make the household members!	2. At night (from 23-7) the tariff is 4 times less than in the daytime.
3. Wipe off dust from light bulbs, To make them shine brighter!	3. It is known that a well-wiped light bulb shines 10% brighter!
4. Incandescent lamps They replaced with energy saving ones, So that they do not warm And more shone.	4. A 12 W energy saving lamp provides as much light as a 60 W lamp. This lamp consumes energy for light, not heat. It consumes 4-5 times less energy.
5. Standby mode Turn off the devices! To save energy Teach everyone!	5. Appliances in standby mode also consume power.
6. Electrical engineering class "A" buy She is more economical You know that!	6. Additional energy consumption for obsolete equipment is 50%. Class "A" equipment is more modern and better in all characteristics.
7. Refrigerator Put it in a cold place. Work economically Make him!	7. Do not install the refrigerator next to a stove or radiator, this will increase energy consumption by 20%.
8. Save energy! Remove the scale In a clean teapot Boil the tea!	8. A layer of scale impairs the thermal conductivity of the kettle walls.
9. Covers for saucepans You will pick up. With the lid closed Cook food!	9. If the cookware is without a lid, the rapid evaporation of water increases the cooking time and therefore the energy consumption. Three times as much energy is wasted without a cover.

Basic rules for saving energy

Install a two-rate meter.
Replace incandescent bulbs with energy-saving ones, wipe the bulbs from dust more often.
When leaving, turn off the light.
Disconnect standby devices.
Use class "A" electrical engineering.
Place the refrigerator in the coldest place.
The stove must be in good working order. The dishes must be with a lid and fit snugly against the heating elements.
Boil water in a clean, scale-free teapot

- We know that electricity serves people and therefore we must save energy. Electric current is also a great danger to humans.

Young Physicist Tips	Students discuss and compose a memo
1. Do not repair the sockets yourself, Entrust to a specialist!	1. Repairing the outlet may cause a short circuit.
2. Do not touch the power transmission line supports, Always beware of leakage current!	2. There is always a leakage current. In rainy and dusty weather, it increases.
3. You are with a fishing rod under the power line Never walk! Hook the wires Kill, just know!	3. When the object approaches the power line wires at 1m, a breakdown of the air gap may occur. If you hook a wire with a fishing rod, the current will pass through the fishing rod and the human body
4. To the torn and sagging Do not come near the wires! Do no harm to your health! Leave the wire break zone, But not in big steps Go "goose" go!	4. If a wire breaks, electric current will flow over a wide area around where the wire touches the ground. When a person enters this place, a step tension arises between the feet. The larger the step, the more stress.
5. It is dangerous to swim during a thunderstorm, Take shelter in a haystack from the rain!	5. Water is a conductor of electric current. Lightning strikes a conductive area.
6. Going in the car, stop! Don't go outside Wait until the end of the storm!	6. When lightning strikes, the discharge goes over the metal surface. Do not touch metal objects in the machine. Turn off the radio, fold the antenna.
7. Under a lonely tree It's dangerous to sit down Lightning will strike. You can lose your life!	7. A lonely tree is a good lightning rod.
8. Don't be near metal, Go away, Don't hold on to metal!	8. There is a possibility of electric discharge moving through communications.
9. Do not plug in electrical appliances, Even if you want tea!	9. Unplug all electrical appliances during a strong thunderstorm. Especially in countrysidewhere there is no ground.
10. Umbrellas, telephones are dangerous in a thunderstorm. Everyone should know this perfectly!	10. Umbrellas have metal parts, telephones are also dangerous. In the event of a lightning strike, the current through the telephone wires reaches your phone.

Solving experimental problems

Guys, we discussed the rules of safe handling of electric current. Let's experiment with measuring devices and include them in electrical circuitbreaking the rules.

Each group receives a task and equipment. Students perform an experiment, draw conclusions, write down, answer.

Exercise 1.

The student, when measuring the current in a light bulb, by mistake turned on a voltmeter instead of an ammeter. What happened then?

Answer: the light bulb did not light up, almost all the voltage turned out to be on the voltmeter, which has a large resistance

Assignment 2

The student, when measuring the voltage on a light bulb, mistakenly turned on an ammeter instead of a voltmeter. What happened then?

Answer: a very large current has arisen, which can lead to damage to the ammeter, therefore it is necessary to quickly turn off the ammeter (practically a short circuit has occurred, since the resistance of the ammeter is small).

Lesson summary: the teacher assesses the work of the class and individual students, the students respond with what they learned in the lesson.

Learned the rules for saving energy.
Safe handling of electricity outdoors and at home.
Rules of conduct during a thunderstorm.
We repeated the basic formulas.
We solved quality problems.
Performed experimental work.

Vii ... Homework information.

ensuring that children understand the purpose, content and methods of completing the assignment

VIII. Reflection.

Pupils stick a green leaf on the board if they understand the topic; if you don't understand - red; if not understood enough - yellow.