If the power cord is too long, it may cause a safety accident. Electric kettle, rice cooker, rice cooker and other household appliances have relatively high power. We also studied P=U~/R in middle school physics. We know that the greater the power P, the smaller the resistance R, and there must be resistance in the wire, which will also consume electricity. The resistance of a conductor is related to its length and cross-sectional area. If the conductor of household appliances becomes thicker and shorter, the resistance will decrease, the partial pressure of the conductor will also decrease, and the voltage will be concentrated on the electric kettle. Because they are connected in series with the same current, their voltage ratio is equal to their resistance ratio, that is, the greater the resistance, the greater the voltage. When household appliances work, the current of wires and appliances is the same. Because P=UI, the conductor will hardly consume electricity and will not burn out the insulation layer of the conductor.
The length of the power cord produced by regular manufacturers is designed in strict accordance with national standards, and it will not be extended at will according to the convenience of users, so as not to bring security risks to users. In addition, if the power cord is too long, it is easy to trip people, or even drag down electrical appliances and burn people, so the regulations should not be too long.
In a word, it is scientific that the power cord of the hot water kettle is very short, and it is the most reasonable length designed by the manufacturer after comprehensively considering various factors.
I don't know if you have noticed that the power cords of various electrical appliances at home are quite long, basically starting at one meter. Only the electric kettle is short, 50cm is normal, and 30cm is not uncommon. This length often does not reach the wall socket, and it cannot be used without the extension of the patch panel.
So why don't manufacturers design the power cord longer? Is it to sell an extra patch panel?
In fact, this length is stipulated in the national mandatory standard GB 4706. 19-2008 "Special Requirements for Safe Liquid Heaters for Household and Similar Electrical Appliances".
"The power cord of the electric kettle should not be longer than 75cm unless it is a spiral power supply." So the power cord of the electric kettle is always below 75cm.
So how is this length specified? Let's take a look at the cover of standard GB 4706. 19:
"GB" stands for national mandatory standard, which means that there is nothing to discuss and it must be done according to this. Did you see the IDT in the bottom bracket? This means the same, that is, the standard is equivalent to IEC 60335-2- 15: 2005. IEC: As we have already introduced, the International Electrotechnical Commission (IEC) unites with electricians all over the world. So basically, the power cord of electric kettles in the world does not exceed 75cm.
On the one hand, this regulation is for security reasons. If the power cord is too long, people will easily trip over things or walk, which will make hot water flow out and cause danger. On the other hand, the more fundamental reason is that the electric kettle is a high-power electrical appliance, and the rated power often exceeds 1000w or even higher, and the power cord needs to bear a great load. Anyway, the longer the wire, the greater the resistance and the more heat. If the length of the power cord is too long, it may burn out due to heat and cause a fire.
So if the power cord is thicker, can't the resistance be reduced? Can't the power cord be made long without burning out? However, making the power cord thick and long is bound to increase the cost, and the thick and long power cord is not necessarily convenient. On the other hand, the standard stipulates that "it shall not be longer than 75cm", and there is only an upper limit. Whether it is 60cm or 30cm depends on the manufacturer's Liang Mi (xin).
The manufacturer who dares to clamp the power cord to the upper limit of 75cm at least shows that he has confidence in the copper core thickness of the power cord.
So when buying an electric kettle, choose a longer power cord, that's right.
The electric kettle has short wires, of course, for safety reasons. As long as the safety is overcome, the wire of this kind of kettle in Japan is 1.3 meters. Why do we only have 0.7 meters? Let's be specific.
At present, even if the kettle has a lid, if you put it down horizontally, hot water will basically flow out. If your hands and feet scratch the power cord and drag the kettle down, more water will flow out under the impact, and boiling water will burn you.
After the household kettle wire is designed to be 0.7 meters, whether it is placed on the kitchen table or on the ground or plugged into a socket about 30 centimeters high, the distance between the kettle and the wall is a little more than 30 centimeters. The closer it is to the wall, the lower the risk of the wire being scratched or falling to the ground, and the safer it is for the user.
I have lived in Japan for a long time. There are 0.75 meters of wires and 1.3 meters of electric kettles, which are similar to those in China. The former is an old product that pours water directly out.
The latter adds security measures. When pouring water, you have to press the button to get out of the water, so you are not afraid of scalding people, which naturally increases the length of the power cord. In addition, the cover of the water inlet is also guaranteed, and it needs two fingers to force the middle at the same time to open it.
I checked the information. In the past six months, 106 people in Japan went to the hospital for treatment because they were scalded by the kettle, all because the kettle was scalded by tap water. Later, they sued the merchants for design defects, which increased security.
Regarding the cost, some people think that shortening the power cord will reduce the cost. In fact, businesses make products according to the instructions. Just like the case of TV is plastic, it is for insulation and safety, not to save the iron, and the bumper of Japanese car.
Why is the string of the kettle always so short? There are three reasons to explain this problem.
First, it is a security issue. The power of the kettle is too high, generally1500-2000 W W. When the power is high, the current will be high and the resistance will be high. If the wire is too long, it will burn easily and cause a fire.
Second, it is also a security issue. The wire is too short to put the kettle on the ground, because the water in the kettle will leak to the ground when it is boiled, and it is easy to get an electric shock when boiling water on the ground.
Third, it is still a security issue. Another advantage of short wires is that they must be placed on a relatively high table against the wall, which is not easy for children to touch, so as not to cause unnecessary harm to children.
To tell the truth, I don't need an electric kettle to boil water now, because drinking it will hurt the fire and even make me constipated. Electric boiling water is definitely not as good as gas boiling water, and gas boiling water is not as good as coal boiling water. It is best to drink the healthiest water. Of course it belongs to wood, fire and water. It is transformed step by step. Wood can be turned into coal, coal into gas, and gas into electricity. Burning coal and firewood is very troublesome now. If you don't have the leisure time, you will have to make do with gas.
I'm Mumu Nokawa. If you have different opinions, please leave a message in the comments section.
Short lines can be more convenient to carry!
In fact, it is to reduce costs. Short wires not only reduce the cost by reducing the wire length, but also can choose a thinner wire diameter after the length is shortened. The cost is lower! Market economy, mass production, each line saves a dime, and thousands of pieces add up, which is not a small number!
This question is good! This question is like a brain teaser, testing your IQ! I have called the Royal Swedish Academy of Science, and the next Nobel Prize in Physics will be a required question! Why? Students, look at the blackboard!
Don't answer the question directly yet! Let's talk about some assumptions first: if the power cord of the electric kettle is not 75 cm but more than 75 meters! Imagine (think hard) that you are sitting on a pot of water at home and plugging it in the unit. Most people like to take advantage of the public, and you can save a lot of electricity in a year! How long will it take you to calculate, and this pot of water will boil! Do you want to go home and fill it up before the water boils? Or wait for him to turn it on, unplug it and pour water? If the former walks home and the water is boiling, you can take down the pot and fill it with water. Who will help you unplug the other end of the unit? If the manager or supervisor passes by at this moment, shout whose plug is this? I think your colleagues will definitely give up on you! It's not worth risking being fired for boiling a pot of water! If it is the latter, once you guess that the water is boiling, unplug it before going home for irrigation, it is a big mistake! Back home, the water hasn't boiled or boiled, and it's cold again! Are you going back to burn again? Or just drinking, neither too hot nor too cold? Don't you think this question is nerve-racking? So I want to suggest that it should be a compulsory topic for the next Nobel Prize in Physics!
In view of the above two situations, the wire of the electric kettle should be shortened, not one meter 75 cm, so that you can keep in front of it to connect and disconnect water at any time, without delaying your drinking and wasting your electricity bill! Isn't this the best of both worlds?
Safety first, saving money second.
All the answers are unreliable. In fact, it is just to cut corners for cost. An electric kettle costs tens of dollars, and the profit is very low. Therefore, the cost must be reduced, and the power cord is short and aluminum. The actual length has little to do with the current. As long as it is thick enough, a few meters doesn't matter. The current of the induction cooker is also large, but the wire is longer.
Kettle is a small appliance commonly used in our daily life. As the landlord said, basically all brands of kettle wires are very short, and sometimes they want to be plugged into a nearby wall socket. The wire is not long enough to be used, so it can only be plugged through the switch!
Electric kettle is a common small household appliance in our daily life, which is related to our safety.
I really haven't paid attention to why the line of the kettle can't be designed longer and easier to use. In order to answer this question, I specially inquired about the relevant standard texts and analyzed them from a professional perspective with my own professional knowledge, mainly for the following two reasons:
1, mandatory requirements of national standards for kettle products
Electric kettle belongs to the national 3C compulsory certification electrical products, and must meet the requirements of relevant national standards, otherwise it will be regarded as unqualified products. According to the national standard GB4706. 19-2008 "Special Requirements for Safe Liquid Heaters for Household and Similar Electrical Appliances", if the power cord of the electric kettle is not spiral, its length should not exceed 75cm.
Now all thermos bottles are no more than 75 cm.
Similarly, there is no such regulation in China, and there are consistent requirements for electric kettles internationally. For example, the international standard IEC 60335-2- 15.2005 and the European standard EN 13750-2002 "Household Kettle for Stove, Cooker or Stand". Definition, requirements and test methods all set hard rules for the production and design of electric kettle. In fact, the national standard is formulated and implemented with reference to relevant international/European standards.
The national standard is reasonable for the length of electric wire of electric kettle. When the electric kettle is working, it is easy for people to trip when walking, resulting in water leakage in the kettle, which may lead to short circuit danger or unnecessary personal injury.
2. From the perspective of security.
Electric kettle is a high-power electrical appliance, and its power is generally above 1500W, which translates into a rated working current of about1500/220 = 6.8a. Under such a large working current, the conductor loss is definitely not small. The greater the loss, the more serious the fever, and there is a risk of fire caused by spontaneous combustion.
According to Ohm's law, U=IR, and the conductor loss P = I * I * R. Under a certain current, the greater the conductor resistance, the greater its loss. In order to reduce the loss, the resistance of the conductor must be controlled.
Ohm's law is applicable to the design of any household appliances.
And the resistance of the wire R=ρL/S, where ρ is the resistivity of the wire, l is the length of the wire, and s is the cross-sectional area of the wire. In order to reduce the resistance of the conductor, the most directly available method is to reduce the length of the conductor L, which is also the fundamental reason why the conductor length of the electric kettle is adjusted within a certain range.
Another feasible way is to increase the cross-sectional area of the conductor, which can also reduce the resistance of the conductor, but the corresponding cost will also increase after the conductor is thickened, because the core of the conductor is copper, and the cost is relatively high. On the other hand, if the wire is too thick, it will not be used in daily life.
In short, our daily life also contains many applications of scientific knowledge, and so does the simple question of the length of the electric kettle, which is indispensable in our daily life. Through the above answers, do you understand the reason?
When using the electric kettle, we often find that the wire of the electric kettle is very short and can only be placed next to the electric plug board. Then why is the wire of the electric kettle so short?
The first is from the perspective of security. Because the electric kettle essentially uses high-power resistance wire to heat and boil water, the calculation formula of power is:
P=UI=U square /r, obviously the smaller the resistance r, the greater the power. Therefore, the resistance of the lead wire must be very small. According to the law of resistance, when using the same copper wire, the resistance is directly proportional to the length and inversely proportional to the cross-sectional area. It can be seen that it is thick and short, with less fever, less temperature rise and long service life. So the wire of the electric kettle you see is thick and short.
One more thing, every centimeter of wire has a cost. In order to save the appearance cost to the greatest extent and win by price in the market competition, the shorter the wire, the better.
Sanyibao in the new era and new financial management I remind you that the operation of electric kettle must be standardized and safety should be the first.