"Safe Use of Electricity" PPT Courseware for Daily Use of Electricity 4

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"Safe Use of Electricity" PPT Courseware for Daily Use of Electricity 4

Short story: Xiaohong buys batteries

The battery of Xiaohong's TV remote control was out of power. Her father asked Xiaohong to go to the supermarket to buy two batteries, but Xiaohong hesitated for a long time and didn't do anything. When asked why, she said she didn't dare because she was afraid that the battery would be charged. .

"The human body is a conductor. I have to hold the battery with my hands. What should I do if I get an electric shock?"

1. The degree of damage caused by electricity to the human body is related to the size and duration of the current passing through the human body.

1 mA current passes through the human body and it feels numb

10 mA Difficult to get rid of by human hands

100 mA Short-term dyspnea

2. The size of the electric shock current is determined by the resistance of the human body and the voltage applied across the human body.

The resistance of the human body is about 104 ~ 105 W; when the skin is moist, the resistance of the human body can be reduced to about 103 W.

1. The higher the voltage, the more dangerous it is

Question 1: Read pages 113~114 of the textbook and discuss in groups: Does the voltage level have anything to do with whether it is dangerous? Why is higher voltage more dangerous?

According to Ohm's law, when the resistance is constant, the higher the voltage, the greater the harm to human life.

Safety voltage: no higher than 36V

2. Common electric shock accidents

The voltage of household circuits is 220 V, which is far beyond the safe voltage. Once an electric shock occurs, it is likely to be life-threatening.

Question 2: Read page 113 of the textbook and discuss in groups: ① What is the cause of electric shock? Compare the two situations of electric shock, carefully observe the similarities that cause electric shock accidents in the two pictures, and summarize the causes of low-voltage electric shock accidents.

①What happened to the electric shock?

Excessive current passes through the human body

Causes of low voltage electric shock:

The human body touches the line of fire and forms a path

②What are the ways of low-voltage electric shock?

Single line electric shock and double line electric shock

High voltage electric shock

1. Arc electric shock: When the distance between a person and a high-voltage charged body reaches a certain value, a discharge will occur between the high-voltage charged body and the human body, resulting in electric shock.

2. Step voltage electric shock: When a high-voltage wire falls on the ground, voltage exists between points at different distances from the high-voltage wire. When there is a large enough voltage between a person's feet, a step voltage electric shock will occur.

In order to prevent electric shock accidents, what issues do you think should be paid attention to when using electricity at home?

Principles of safe electricity use:

◆Do not come into contact with low-voltage charged objects, and do not approach high-voltage charged objects.

◆Replace light bulbs and turn off the power switch before moving electrical appliances.

◆Do not get the electrical appliance wet or damage the insulation layer.

◆Fuses, sockets, wires, household appliances, etc. should be replaced in time when they have reached the end of their service life.

Taking stock of harvest

What knowledge did you learn through today's study? Speak up and share the joy of harvest with everyone!

1. The correct way to do the following is ( )

A. Use scissors or pliers with damaged insulating handles to cut live wires

B. Drying clothes on the wire

C. When you find someone getting an electric shock, you should immediately pull the person who got the electric shock away from the electrified object with your hands.

D. If you find the severed ends of power lines falling on the ground, don’t get close to them, let alone pick them up.

2. Which of the following statements is incorrect? ( )

A. On thunderstorm days, do not take shelter under a big tree

B. Do not use a wet cloth to clean a burning lamp

C. When moving electrical appliances, disconnect them from the power source first.

D. When a fire occurs due to a short circuit in a transmission line, pour water immediately to extinguish the fire.

3. On a thunderstorm day, a villager went to take shelter under a big tree. Unfortunately, he was struck by lightning and was seriously injured. After that, rumors spread in the village, saying that he was "haunted by devils", that he "did not practice well in his previous life", etc., at home. People cannot hold their heads up in front of everyone. Instead of sending patients to the hospital for treatment, they pray to God and worship Buddha, causing patients to delay treatment.

(1) Are the views stated in the article correct? ____________________________.

(2) In order to avoid similar accidents, people installed __________________ on tall buildings.

(3) If you encounter such thunderstorm weather conditions, what you should do is_______________.

Homework:

1. Investigate ways to prevent electric shock in daily life. How to prevent electric shock from the electrical appliances in your home?

2. Complete the exercises after this lesson.

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Update Time: 2024-10-07

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