We are used to it, and we are used to the five-hole socket. In the case of a five-hole socket, it is divided into two parts, one of which is two holes and one part of which is three holes. Correspondingly, there are also two kinds of plugs, which are a two-pin plug and a three-pin plug. I don't know if you have thought about it. What is the difference between a two-pin plug and a three-pin plug? Why are some appliances with three-pin plugs and some two-pin plugs? what differences are there?
Two-legged plug
In fact, the two-pin plug can be used normally for most appliances. We use electricity on a daily basis, mostly for single-phase AC. Two pins, which are connected to the neutral wire and the live wire, respectively, can operate normally.
In addition to the products that must be used as described below, the manufacturer must use a three-pin plug in order to save costs. Need to know that the two-pin plug product, replaced by a three-pin plug, can be used normally. The reason why you don't need a three-pin plug is to reduce costs!
What kind of equipment does it have to use a three-pin plug? Some people think that it is judged according to the power level. Actually, for example, the induction cooker mostly uses two-pin plugs. A three-prong plug is required only in the following two cases.
First, the metal shell
The one that the three-pin plug has more than the two-pin plug is the ground wire. The ground wire is often connected to the electrical enclosure. The two-pin plug product can be used normally. But when there is a leakage in the circuit, there is a possibility that electricity will reach people.
In the case of a product with a grounded casing, the current will flow along the ground to the ground (the earth potential is lower) after the leakage, so that it will not cause harm to people.
Housings made of metal or other materials with good electrical conductivity tend to charge the casing when leakage occurs, which may result in greater potential for electric shock. Therefore, the electrical appliance of the metal casing or the conductive casing must use a three-prong plug and be properly grounded.
Plastic casings or other insulating casings, because of their good insulation properties, even if there is leakage inside, the probability of electricity to people is relatively small, so there is no need to ground.
Second, the electrical inside needs to distinguish between zero fire lines
Some appliances need to distinguish between neutral and fire lines at work. For example, an electrical appliance with a switch needs to connect the upper port of the switch to the live wire.
The two-pin plug can be easily inserted into the socket due to the left and right, so it is difficult to distinguish between the zero line and the live line. The three-pin plug, due to its triangular nature, determines the position of each pin is fixed. When the socket is wired, there is a "left zero right fire" rule. Therefore, the lower left pin of the three-pin plug must be connected to the neutral line, and the lower right pin must be connected to the live line. In this way, the inside of the electrical appliance can easily distinguish the zero fire line.
Education Projector
Educational projectors are mainly aimed at classroom teaching by school teachers; traditional projectors are not easy to carry. Due to the naughty students in school classrooms, projectors are not safe to place in classrooms and are easily damaged by students. The portability of educational micro-projectors makes up for teaching Vacancy, it is convenient for teachers to give lectures and only need to store the materials in the projector and show them to students for teaching, saving the trouble of textbooks and handwriting with pens and chalks. Its general weight will not exceed 0.2Kg, and some do not even need fan cooling or ultra-small silent fan cooling.
Educational projectors need to have:
1. Clear handwriting Educational projectors most often display text and images, at least a resolution of 1024*768 or more, and a contrast ratio of more than 3000 lumens, so that students in the back row can see the projection clearly
2. Short-focus large screen;
3. Accurate color;
4. Easy operation;
5. Features such as multiple connection methods.
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