Lightning strike knowledge

Popularization of lightning protection knowledge

Brief introduction of lightning strike

In fact, lightning is a huge electric spark. This is obvious when lightning rushes from the ground to the clouds or from the clouds to the ground, although it can also spread in or between clouds. The airflow that makes up a storm cloud can separate powerful electric energy from the cloud.

Positive current is concentrated in the lower part of the cloud, and negative current is concentrated in the upper part of the cloud or on the ground. Just like electromagnetism, positive and negative electricity attract each other. After continuous transmission, positive and negative currents collide, forming a huge electric spark, thus forming lightning.

Because the speed of light is about 6.5438+0 million times that of sound, there will be a certain time difference between lightning and accompanying thunder. The distance between you and the storm can be calculated by counting the seconds of the time difference between lightning and thunder, and then dividing by 5 meters. The number is the number of miles you are away from the storm, that is, your distance from the storm (miles) = the time difference between lightning and thunder (seconds) /5 (meters).

Lightning strikes millions of volts, causing air to expand and explode, thus forming lightning. Thunder itself is harmless. The possibility of being struck by lightning in thunderstorm weather is very small, but the lightning phenomenon cannot be predicted completely and accurately, so be careful to prevent and reduce the danger.

Lightning always twists and turns along the path of least resistance. Its path in the air depends entirely on the electric field and charge distribution in the air, and it is usually only affected by the ground conditions when it is more than ten meters away from the ground to 100 meters. Generally speaking, the ground has good conductivity and there are prominent tall objects. , vulnerable to lightning. For example, the geological conditions of metal minerals with good conductivity are more vulnerable to lightning strikes than general geological conditions, and the chances of being struck by lightning in wet soil are more than in dry soil, sandy land and rocky land. The water surface is more vulnerable to lightning strikes than in dry land, and prominent buildings such as tall buildings and chimneys are more vulnerable to lightning strikes than in flat land, and mountainous areas are more vulnerable to lightning strikes than in valleys.

Four ways of lightning hurting people

There are four forms of lightning damage to people, namely: direct lightning strike, contact voltage, side lightning strike and step voltage.

Direct lightning: When lightning happens, it directly hits the human body, because people are good conductors, and lightning current as high as tens of thousands to hundreds of thousands of amperes flows from the top of people's heads through the human body to their feet and into the earth. People were struck by lightning, injured by lightning, and even died seriously.

Contact voltage: When lightning current discharges through tall objects, such as tall buildings, trees and metal structures. Powerful lightning current will produce tens of thousands to hundreds of thousands of volts on tall conductors. When people accidentally touch these objects, they will be attacked by this touch voltage and get an electric shock accident.

Side lightning strike: When lightning strikes an object, strong lightning current discharges to the earth through the object. Generally speaking, current is the easiest to flow through a channel with low resistance. The resistance of human body is very small. If a person is near an object struck by lightning, lightning current will break through the air near the height of the person's head and then be discharged through the human body. Make people under attack.

Step voltage: When lightning is released from the cloud to the earth, it will produce a potential field. The distribution of potential is that the closer to the lightning point on the ground, the higher the potential; The potential far away from the lightning strike point is low. If the site potentials of people's feet are different when lightning strikes, this potential difference will generate voltage between people's feet, and there will be current passing through people's lower limbs. The greater the distance between legs, the greater the step voltage.

In view of the above four ways of lighting people, corresponding measures should be taken to prevent them under various circumstances.

What kind of people are vulnerable to lightning?

The maximum probability of a person being struck by lightning is1∶ 600,000. The number of lightning itself has not increased, it is 8 million times a day. According to the statistics of insurance companies, about 600 people are struck by lightning every year, and now it has increased to 1500. Some scientists blame this on the male hormone testosterone. Because 86% of people who are struck by lightning are men. They stressed that in a group of people, people with more testosterone are more likely to be struck by lightning.

Why can people who have been struck by lightning still live? It should be said that tens of millions of volts of charge and hundreds of thousands of amperes of current can kill people in an instant, but some people survived. Some people think that lightning is different from bare wire. Sometimes lightning doesn't even leave any trace on the body, but it penetrates the internal organs. Or on the contrary, just passing by and burning clothes and shoes. Powerful current sometimes "blows through" the whole body in a few millionths of a second, so it is impossible to burn to ashes all the time. The key is to look at the average resistance of organs and tissues in the body of 700 ohms. The greater the resistance, the more serious the consequences. When a person is struck by lightning, the first thing that "catches fire" is the nerve fiber, that is, the circuit in the body, but at most its protective film is damaged, which is essentially similar to the insulator in the wire. After being hit by lightning and returning to normal, people don't even feel any change. Sometimes it takes months to feel it, and then the nerve fibers start to "shorten" and make contact in some places where they shouldn't.

safety regulations

General principles: First, the position of the human body should be as low as possible to reduce the risk of being directly struck by lightning; Second, the contact parts between the human body and the ground, such as feet, should be as close as possible, and the smaller the contact with the ground, the better, so as to reduce the "step voltage".

1. Feeling skin tingling or hair standing on end during thunder and lightning is a harbinger of lightning and should be avoided immediately. If you can't avoid it, get close to the ground immediately. People who are struck by lightning may be burned or severely shocked, but they will not be prosecuted and can receive treatment safely.

If you are in tall objects such as trees and buildings, you should leave immediately. If it is too late to leave tall objects, find some dry insulation on the ground, sit on it, take a squat lightning protection posture, and pay attention to your feet together. Put your hands together. Never put them on the ground. Never lie down. At this time, although the height is reduced, the danger of "step voltage" is increased. Water can conduct electricity, so wet objects are not insulated.

3. Don't avoid the mouth of the cave, under big rocks or hanging rocks during a thunderstorm, because these places will become spark gaps, and the arc generated when the current passes will hurt people. But the deep hole is safe, so you should try to go inside. Try to hide in the depths of the cave. Keep your feet together and don't touch the cave wall. At the same time, you should also take off your metal objects, such as watches, rings, earrings, necklaces and other items, leave your body and put them aside.

4. Stay away from iron bars and other metal objects. What is fatal is not direct electric shock. After lightning hits the conductor, it instantly releases electric energy, and the arc emitted to both sides reaches several meters. In addition, hot lightning makes the surrounding air expand rapidly, producing shock waves. The sound made by these shock waves is thunder. If you hear it nearby, powerful sound waves may impact the lungs, which can cause death in severe cases.

If you are in an open place during a thunderstorm, you should immediately squat down on the ground, which can reduce the risk of being struck by lightning. Don't support the ground with your hands, which will expand the contact range between your body and the ground and increase the risk of being struck by lightning. Hold your knees with your hands, keep your chest close to your knees, and keep your head as low as possible, because your head is the most vulnerable to lightning.

6. Solitary trees and isolated grass sheds in open areas and hilltops should be avoided because they are vulnerable to lightning strikes. It is dangerous to take shelter from the rain at this time, especially standing under low branches that extend far to both sides. However, things are divided into two parts. If there is a dense forest in the wild and there is no other lightning protection place for the time being, then you can also use the dense forest to prevent lightning, because the probability of being struck by lightning is similar everywhere in the dense forest. At this time, as long as you don't stand on the edge of the forest, you'd better choose an open space in the forest, keep your feet together and keep a close distance from the surrounding trees.

7. In principle, during lightning, you should try to avoid tall objects without lightning protection equipment, such as towers, large cranes, haystacks, tents, etc. in open areas, and don't go to commanding heights such as mountain tops and ridges. Do not go near any part of lightning protection equipment. Railways, long metal railings and other huge metal objects should also be avoided.

8. If you swim in rivers, lakes or swimming pools, you should go ashore and leave in thunderstorm weather. Because the water surface is easily hit by lightning, and if it is injured by lightning in the water, it will increase the risk of drowning. In addition, try not to stay on ships without lightning protection equipment, especially wooden sailboats with high masts.

9. If you are driving, you should stay in the car. The car shell is made of metal. Because of the shielding effect, even if lightning hits the car, it will not hurt people. Therefore, the carriage is an ideal place to avoid lightning. However, it is best not to ride horses, bicycles, motorcycles or tractors during lightning.

Code for outdoor lightning protection

To ensure safety, the following rules should be observed outdoors:

1. Don't stay on the high-rise platform in thunderstorm weather, and don't enter isolated shacks, sentry boxes, etc. In the open air.

2. Stay away from the exposed water pipes, gas pipes and other metal objects and power equipment in the building.

3. It is not advisable to hide under the big tree during a thunderstorm. If necessary, you must keep a distance of 3 meters from your torso, squat down and put your legs together. These trees and rocks are safer when the height is below1/5 ~110.

4. If there are ants crawling on your head, neck and hands when thunder and lightning strike, and your hair stands on end, it means that lightning is coming. Get down on the ground quickly to reduce the risk of being struck by lightning, and take away the metal ornaments, hairpins and necklaces you wear. Take all the metal things with you and put them in your backpack, especially the glasses with metal frames. Do not approach any part of lightning protection equipment; Try not to use radios and televisions with external antennas, and don't answer mobile phones.

If it is too late to leave a tall object in the outdoor thunderstorm, you should immediately find some dry insulation and sit on it with your feet crossed. Never put your feet on the ground outside insulation, because water can conduct electricity.

6. When avoiding thunderstorm outdoors, be careful not to hold the ground with your hands. At the same time, put your hands on your knees, keep your chest close to your knees, and try to keep your head down, because your head is more vulnerable to lightning than other parts of your body.

7. When you hear thunder within a few seconds after seeing lightning outdoors, it means that you are in a dangerous environment near a thunderstorm. At this time, you should stop walking, put your feet together and squat down immediately. Don't pull together with others, keep a certain distance from each other, and avoid being directly infected by lightning. It is best to use plastic rain gear, raincoat, etc.

8. In thunderstorm weather, it is not advisable to open an umbrella or hold high badminton rackets, golf clubs and hoes in the wild. Not suitable for outdoor ball games. It is very dangerous to play golf and football in thunderstorm weather. It is not advisable to stay on the water surface or water edge; It is not advisable to wash clothes, fish, swim or play by the river.

9. In thunderstorm weather, it is not advisable to drive a motorcycle, ride a bicycle or run fast in the rain, because the greater the stride of the body, the greater the voltage, and the easier it is to hurt people.

10. If you see a high-voltage line that is broken by lightning outdoors, you should be vigilant at this time, because there is a step voltage near the breakpoint of the high-voltage line. People nearby must not run at this time, but should jump off the scene with their feet together.

Lightning rescue

Being struck by lightning is not necessarily fatal. Many people survived the catastrophe, feeling only electric shock and minor burns. Others who are struck by lightning may cause fractures (muscle spasm caused by electric shock), severe burns and other injuries.

Lightning damage often happens, and it will be greatly threatened if it is not avoided or lightning protection measures are improper. It is reported that in Switzerland, about 10 people per million people are struck by lightning every year. In the United States, more people die from lightning accidents than from hurricanes every year; In Japan, a lightning accident occurred in 1968, resulting in the death of 1 1 children. Therefore, it is necessary for us to know the specific measures of lightning protection and the rescue methods after being struck by lightning.

Lightning hurts people mainly because the lightning current is strong. Its main harm to human body. Usually it's not a burn. If lightning hits the head and reaches the ground through the body, it will paralyze people's nerves and heart, which is likely to be fatal. When people are impacted by lightning current, their hearts either stop beating or the beating rate is extremely irregular, resulting in vibration. In both cases, blood circulation will be stopped and brain nerve will be damaged, and people will die within a few minutes. It is still possible to wake up after being rescued by lightning in time. Sometimes even if you can't feel the victim's breathing and pulse, it doesn't necessarily mean "death". If you can rescue in time (such as artificial respiration), you can often restore the heartbeat and breathing of the "dead". In addition, lightning strike may cause the injured person's clothes to catch fire, and may also melt the injured person's metal ornaments and watchbands.

When the human body is struck by lightning, it is often felt that there is still electricity on the person struck by lightning, and the rescue time is delayed because he is afraid to rescue. In fact, this concept is wrong. If there is a state of "suspended animation" caused by lightning strike, the following rescue methods can be taken. If the electrocuted person loses consciousness, keep him in a horizontal posture and keep him warm and comfortable. It is very necessary to carry out electric shock first aid and artificial respiration immediately.

1. mouth-to-mouth resuscitation. The sooner artificial respiration is given after lightning strike, the better the recovery of the injured person's body, because people who lack oxygen for more than ten minutes will be fatal. If you can save your heart with cardiopulmonary resuscitation within 4 minutes, there may still be time to save it.

2. Give heart massage to the injured, and promptly notify the hospital for first aid. If a group of people are struck by lightning, it doesn't matter who groans. First, save those who can't make a sound.

If the injured person's clothes catch fire, let him lie down immediately so that the flame won't burn his face. Otherwise, the injured person may die from lack of oxygen or burns. You can also splash water on the injured, or wrap the injured with thick coats and blankets to put out the flames. The injured should not run because of panic, which will make the fire burn more and more brightly. They can roll on the ground to put out the fire, or they can lie down in a depression or pool with water to put out the fire. Cool the wound with cold water and then cover it with a dressing, for example, wash one side with a folded handkerchief and cover it with a clean cloth.

Attachment: the general law of astronomical phenomena

A. Signs of better weather

1. During the day, the valley breeze usually blows from the bottom up, but at night it is just the opposite, usually blowing from the top of the mountain to the bottom of the valley.

2. During the day (especially in the morning), you can see that the clouds in the mountain pass gradually divide into fog and gradually dissipate.

3. At sunset in the evening, an orange or rose sunset (flaming clouds) appeared over the western valley.

There is fog at the foot of the mountain in the evening, and the weather is cold (cold at night), which means that the weather may be better the next day.

There is dew and frost on the grass in the morning. 6. The starlight is stable and rarely flashes.

B. signs of bad weather

1. The valley breeze blows from the top of the mountain to the valley during the day and from the valley to the top of the mountain at night.

2. Silk clouds appear in the morning, and then black clouds increase and slowly sink.

3. The cloud moves very fast and tends to increase, which may be a precursor to the storm.

The wind direction changes suddenly, becoming bigger and bigger, accompanied by dark clouds.

5. After dry heat or fog, the visibility suddenly increases.

The fog filled the valley in the morning and still lingered at night.

7. There is a big halo around the sun during the day and a small halo around the moon at night, which is a sign of strong wind.

8. The stars twinkle before dawn.

9. The temperature rises in the evening and the night is warm and sultry.

10. The rising clouds in the half valley may be a sign of future storms.

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Tourists use mobile phones to trigger lightning strikes on the Great Wall.

Author: Lu Source: Jinghua Times Editor: A Jun

In response to the lightning strike of some tourists on the Juyongguan Great Wall on the 23rd, the office of the Ming Tombs Special Zone in Changping District invited the director of the Meteorological Bureau of Changping District and several meteorologists to the scene yesterday to analyze the reasons why tourists were struck by lightning. After investigation by experts, it is believed that the lightning strike of tourists is induced lightning caused by using mobile phones in thunderstorm weather.

According to the layout of lightning protection facilities on site, tourists above and below the lighthouse area where tourists were struck by lightning were not struck by lightning, and the situation of tourists using mobile phones at the time of the incident, experts believe that the use of mobile phones to induce lightning in thunderstorm weather is the main reason for lightning attacks on tourists.

According to experts, mobile phone electromagnetic wave is a good conductor of lightning, which can collect and guide lightning on a large scale. When using a mobile phone, the mobile phone will emit electromagnetic waves, which will easily cause lightning strikes when it encounters high-altitude downward current; In thunderstorm weather, it is easy to induce lightning when the mobile phone is turned on, but using the mobile phone in lightning strike area undoubtedly acts as a lightning rod. And according to research, if the cell phone signal is too strong, sometimes even the lightning rod doesn't work. Therefore, experts remind citizens and tourists not to use mobile phones during lightning, especially in places where the terrain is relatively empty and there are no tall buildings around.

According to the person in charge of the Ming Tombs Special Zone Office and Juyongguan Great Wall Management Office, Juyongguan Great Wall Scenic Area has installed 13 lightning protection facilities. At the same time, the office of the Ming Tombs Special Zone also said that the lightning strike caused great shock to the office and Juyongguan Great Wall Management Office. In the future, they will add warning signs in eye-catching places of tourist attractions to publicize lightning protection knowledge such as turning off mobile phones in thunderstorm weather. In strong thunderstorm weather, tourists should be discouraged from entering the city and climbing mountains, and at the same time, guidance should be strengthened to avoid similar tragedies from happening again.

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Zhang Mingying, an expert from the Municipal Meteorological Observatory, said that in the process of discharging between clouds, the instantaneous energy is particularly large. Some thunderstorms instantly release more energy than Gezhouba Power Plant does at the same time. If they fall to the ground, they will destroy houses, kill people and animals and cause fires. Yesterday (August, 2005) at around 1, a Greek female tourist who was visiting the Great Wall at Simatai, Miyun 1 1 beacon tower died on the spot due to lightning strike.

When there is lightning and thunder, try not to move outdoors, especially under trees or high-voltage lines. In addition, when it thunders in the open field, remember not to run fast, but to walk slowly, because the faster you run, the greater the step voltage, which will become a lightning rod and be prone to danger. At the same time, try not to use your mobile phone when it thunders.

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On July 23rd, 2004 14: 40, the Juyongguan Great Wall was suddenly hit by a thunderstorm. Dozens of tourists went to the beacon tower to take shelter from the rain, and a thunder knocked them to the ground. Some people lost consciousness instantly, and at least 15 people were admitted to hospital due to injuries. Experts from Changping Meteorological Bureau visited the site and thought that tourists were struck by lightning because they used mobile phones to cause induction lightning in thunderstorm weather. Some meteorologists have analyzed that the atmospheric electric field always exists whether it is dark clouds or sunny days. Mountainous areas, river banks, lakes and other places are high-incidence areas of lightning. Lightning disaster is mainly formed by the discharge process between cloud and ground. The higher the ground, the better the conductivity, and the easier it is to become the lightning strike point.

Expert tips

During the thunderstorm season in summer, lightning disasters are on the rise, and some famous scenic spots in China have lightning accidents every year. For outdoor tourists, beware of lightning strikes when traveling. Experts remind citizens and tourists not to use mobile phones in areas with empty terrain and no tall buildings around. Don't take shelter from the rain near power sources, trees and telephone poles, and avoid places with water such as lakes and swamps and isolated buildings such as thatched sheds, huts and pavilions that are vulnerable to lightning strikes. Look for low-lying places, put your feet together, take a squat posture, and try to reduce your body height. Don't carry an umbrella with a metal skeleton in an open place. It is not suitable to use and contact electrical equipment in thunderstorm weather to avoid lightning disaster to the maximum extent.

I hope it will help you, and we will work together on the way to study.