Switches and Fuses 开关和保险丝
文章来源:未知 文章作者:meng 发布时间:2009-10-28 05:55 字体: [ ]  进入论坛

An electric switch is often on a wall near the door of a room. Two wires lead to the lamp in the room. The switch is fixed1 in one of them. The switch can cause a break in this wire, and then the light goes. The switch can also join the two parts of the wire again, then we get a light.  

Switch can control many different things. Small switches control lamps and radio sets because these do not take a large current(电流), larger switches control electric fires(电热器). Other switches can control electric motors.

Good switches move quickly. They have to stop the current suddenly. If they move slowly, an electric spark appears. It jumps across the space between the two ends of the wire. This is unsafe and it heats the switch. Very big switches are sometimes placed in oil, Sparks do not easily jump through oil, and so the oil makes the switch safer.

A large current makes a wire hot. If the wire is very thin, even a small current makes it hot. This happens in an electric lamp.

The electric wires in a house are covered with some kind of insulation2(绝缘). No current can flow through the insulation, so the current can never flow straight from one wire to the other, but the insulation on old wires is often broken, then the copper3 of the two wires can touch. A large current may flow, and if this happens, the wires will get very hot. Then the house may catch fire.

Fuses5(保险丝) can stop this trouble. A fuse4 is only a thin wire which is easily melted. It is fixed in a fuse-holder6(保险盒). The fuse-holder is made of some material which cannot burn. A large current makes the fuse hot and then it melts away. We say that the fuse "blows(保险丝烧断)". The wire is broken and no current can flow. So the house does not catch fire, but all the lights and electric fires go out(熄灭) because there is no current.

When a fuse blows, something is wrong. We must find the fault first. Perhaps two wires are touching7. We must cover them with new insulation of some kind. Then we must find the blown fuse and repair it. We put a new piece of fuse-wire in the holder. (Sometimes we can find the right fuse- holder because it is rather warm, but the others are cold.) If we do not repair the fault first, the new fuse will blow immediately.

Some men get angry when a fuse blow. So they put a thick copper wire in the fuse-holder! Of course this does not easily melt; if the current rises suddenly, nothing stops it. The thick wire easily carries it. Then the wires of the house may get very hot and the house may catch fire. Some of the people in it may not be able to escape. They may lose their lives. So it is always best to use proper fuse-wire. This will keep everyone and everything in the house safe.


1 fixed JsKzzj     
  • Have you two fixed on a date for the wedding yet?你们俩选定婚期了吗?
  • Once the aim is fixed,we should not change it arbitrarily.目标一旦确定,我们就不应该随意改变。
2 insulation Q5Jxt     
  • Please examine the insulation of the electric wires in my house.请检查一下我屋子里电线的绝缘情况。
  • It is always difficult to assure good insulation between the electric leads.要保证两个电触头之间有良好的绝缘总是很困难的。
3 copper HZXyU     
  • The students are asked to prove the purity of copper.要求学生们检验铜的纯度。
  • Copper is a good medium for the conduction of heat and electricity.铜是热和电的良导体。
4 fuse BfXz6     
  • The metal will fuse at a relatively low temperature.这金属在不太高的温度下熔化。
  • This is the right fuse for the refrigerator.这是电冰箱上使用的保险丝。
5 fuses 08f805b15677e4ee4603ecc91fec6268     
保险丝( fuse的名词复数 ); 导火线; 引信
  • The author skillfully fuses these fragments into a cohesive whole. 作者将这些片断巧妙地结合成一个连贯的整体。
  • We electrified the main circuits to see if the fuses would blow. 我们把主要电路通上电,看看保险丝是否会烧断。
6 holder wc4xq     
  • The holder of the office of chairman is reponsible for arranging meetings.担任主席职位的人负责安排会议。
  • That runner is the holder of the world record for the hundred-yard dash.那位运动员是一百码赛跑世界纪录的保持者。
7 touching sg6zQ9     
  • It was a touching sight.这是一幅动人的景象。
  • His letter was touching.他的信很感人。
TAG标签: current electric switch fusd