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The World without Lines - Wireless Technology
[277th]Science Story
2009년 12월 18일 (금) 18:26:18 Kim Min-jeong, Reporter yacuza3104@pusan.ac.kr

 

The World without Lines

                     - Wireless Technology

 

   
Changing charge makes a dielectric inner current in the material.

           Do you have an experience playing with a radiotelegraph? When I was a child, I teased my mom to buy a wireless telegraph set. It was very funny and made for curiosity, because I could talk with Mom although I could not see her. That was a little machine made by wireless technology. What do you think about wireless technology? Listen to the radio setting the frequency, call your family through a mobile phone in walking, and enter the Internet through the NESPOT service, the wireless Internet produced by Pusan National University (PNU). How many things can you imagine? Like this, wireless technology provides us with huge conveniences. Don’t you want to know about the principle of the wireless technology? Then, let’s try to understand about it.
          First, we need to know about an electron charge. Many people feel strange about these words “electron charge.” In the dictionary, electron charge means the quantity of electricity that has a matter. It is hard to understand because of the words “the quantity of electricity.” Then, we can understand electron charge through another phenomenon. Maybe you have the experience of hearing the sound ‘tac tac’ when wearing or pulling off shirts or knitwear, or, messing up someone’s hair when rubbing or detaching their hair from a balloon or a plastic sheet. Everyone knows this phenomenon is the effect of static electricity. This effect produces friction between two objects. To understand this effect, we need to know the atom model. An atom is the smallest unit of matter. According to the atom model of Niels Hendrik David Bohr (1885~1962), Danish physicist, an atom is composed of protons, neutrons, and electrons. Protons have a positive charge (+charge) and neutrons have no charge in a nucleus, the center of the atom. Surrounding the atom are orbiting electrons having a negative charge (-charge). Electrons are much lighter than the nucleus, so it is easy to separate electrons from the atom. Materials have its character about to accept electrons. Some materials are easy to accept electrons, but others are easy to discharge. When these neutral materials rub each other, electrons are moving from the discharging material to the accepting. After detaching, the discharging material has a positive charge and the accepting material has a negative charge. These electrified materials have attraction to each others. This is the reason why they stick between the balloon and hair. In short, there is positive charge and negative charge in electron charge, and these two charges produce an electric attraction force. 
          Only one charge exists. There is no force. However, if another charge comes, electric force is immediately produced. This means that original charge has potential energy to produce electric force in its surroundings. This stored potential energy is called “an electric field.” If field difficult to understand? Then, we can understand it through the Earth we live. Everybody knows gravity. When a material is in Earth (gravity field), then it has weight, because Earth pulls it and it pulls Earth. However, when it escapes the gravity field, it floats into the universe, because it gets beyond the limit range of the gravity field. Again, it is comes to earth, it has gravity force to earth immediately by gravity. This means, the Earth has potential energy to produce weight (gravity force) in the air. 
          Now, we can examine the principle of wireless technology. We assume that only one dielectric substance like air, water, or anything, exists. We know that every substance is composed of atoms. Atoms are organized by protons, neutrons, and electrons. Positive charges are put near by the material. Then, this charge makes an electric field, so the electrons of atoms of the substance move forward to a positive charge by attraction force. This effect is called “polarization.” After that, we change the charge from positive to negative. The electrons move in opposite direction by repulsive force. Moving electrons produce a current, so we can produce the current without electric lines. In other words, the used energy for changing charge produces a current in the material. The current is the signal humans can operate, and this is the principle of using wireless communication.

By Kim Min-jeong, Editor-in-Chief
yacuza3104@pusan.ac.kr


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