I don't quite understand the principle of power-saving device, please help me solve it.

What kinds of tableware disinfection cabinets are there? What are their characteristics?

There are three kinds of working principles, namely, the high-temperature type using far-infrared heating elements for high-temperature disinfection, the low-temperature type using ozone generator to generate corona discharge to release ozone for sterilization, and the dual-function tableware disinfection cabinet with high-temperature and ozone functions. The high-temperature type adopts physical disinfection, that is, the tableware is disinfected in a closed room at a high temperature above 120℃ by using the characteristics of fast heating speed and strong penetration of far infrared rays. The first disinfection time is generally less than 25min, and the power consumption is about 0.3 kW·h, which is suitable for the disinfection of high temperature-resistant tableware such as ceramics and metals. The low temperature type is disinfected with ozone, which is a strong oxidant and bactericide. It can enter the cells of bacteria and viruses, destroy their structures and oxidase, and kill bacteria and viruses. Ozone can also spread to all corners of the disinfection room for disinfection, which is suitable for disinfection of tableware and tea sets of any type. The bifunctional model has the characteristics of both.

This is the first time I have seen you.

There are many thunderstorms in summer, so we should pay attention to avoid being injured by lightning.

There are many thunderstorms in summer. At this time, if people don't take appropriate preventive measures when they go out, they are easily struck by lightning. Then, in thunderstorm weather, how should people who are outdoors prevent and avoid lightning strikes? Generally speaking, we can start from the following five aspects:

1. Pay attention to safety and stop outdoor activities as much as possible. You can seek lightning protection places nearby, such as caves and houses, but don't enter low-rise buildings without lightning protection facilities such as shacks and sentry boxes. It is not suitable to enter the metal trunk to avoid thunderstorms, and it is not suitable to hide under big trees.

2. Pay attention to the terrain and try to stay away from the top of the mountain, the water surface or the land-water junction. In the southern water towns of our country, people move frequently at the junction of water and land, so lightning casualties are particularly serious. Every thunderstorm season, tourists must pay attention to stay away from the top of the mountain or other commanding heights when encountering thunderstorm weather; If you are in the forest, pay attention to choose places surrounded by trees and with open spaces in the middle for lightning protection; It is generally safer to enter the cave, but don't lean against it.

3. Keep a good walking state and eliminate potential safety hazards as much as possible. Don't walk in the rain with an umbrella with a metal handle, and don't touch the rails and wires. You can't run in a thunderstorm, and you shouldn't ride a bike, let alone a motorcycle. At the same time, when walking in residential areas to avoid rain, you should try to stay away from exposed metal objects such as water pipes and gas pipes and electrical equipment in buildings.

When lightning strikes or is about to happen, we must consider taking emergency measures. Thunder and lightning, if there are ants crawling on your head, neck and hands and your hair stands on end, it means lightning is going to happen. You should get down on the ground and throw away the metal ornaments, hairpins and necklaces you wear to reduce the risk of being struck by lightning. If you hear thunder within seconds of seeing lightning, it means that you are in a dangerous zone near a thunderstorm. At this time, you should stop walking, put your feet together and squat down immediately. Don't get involved with people. It is best to use plastic rain gear and raincoat.

5. Don't use your cell phone in thunderstorm weather. Experts remind that there are many people surfing the Internet and using mobile phones now, so we must pay attention to thunderstorm weather. Don't surf the Internet in thunderstorm weather, don't use modem or ADSL equipment, it's best to unplug the power socket of the computer and ensure that the computer has a good grounding. It is best to install lightning arrester for household appliances. Don't pull bare metal wires from outdoor to indoor, try not to answer and dial mobile phones, and avoid ordinary phones when they are struck by lightning. Because lightning rods can only protect buildings, they can't do anything about lightning waves invading along overhead lines and telephone lines.

This is the first time I have seen you.

Does the turn-on frequency affect the service life of the lamp?

I'm often asked: I've heard that the life span will be shortened when the lights are turned on and off. From the economic point of view, it is better to turn off the lights at will or not. He said that some time ago, he read a report in the newspaper that an expert told people that the life of a lamp would be shortened by two hours every time it was turned on and off, so he concluded that if it was necessary to turn on the light within two hours, it would be better not to turn it off.

Is this "reasoning" correct? Can the shortened life span of 2 hours be compared with the electricity consumed by turning on the light for 2 hours? We might as well do a calculation.

Let's assume that this is a 36W fluorescent lamp. Based on the current nominal economic life of ordinary fluorescent lamps of 8,000 hours, and the average unit price of lamps is calculated in 8 yuan, the cost of lamps corresponding to 2 hours is 8× 2/8,000 = 0.002 yuan.

Calculated by the most energy-saving electronic ballast, the total power consumption of the system is only 0.036 kW, and the electricity price is 0.60 yuan per kWh, so the electricity fee for two hours is 0.60× 0.036× 2 = 0.043 yuan.

There is no comparison between the two results, so the expert's opinion is wrong.

Even if we agree to shorten the service life of switching primary lamps by 2 hours, the critical value of switching time interval energy consumption cost equivalent to 2 hours service life cost should be: t = 0.002/(0.60× 0.036) = 0.093 hours = 6 minutes.

In other words, if you leave the room for more than 6 minutes, you should turn off the lights.

We can use the same method to calculate the 40W incandescent lamp (unit price 1 yuan, service life 1000 hours). The result is less than 5 minutes apart.

At this point, we just did an arithmetic problem for primary school students according to formal logic. Let's discuss the premise of this hypothesis again: does switching on and off once really affect the life of the lamp for 2 hours?