题干

人类正面临能源危机,为选用节能交通信号灯的灯源,实验室通过实验发现下表中的LED 灯和白炽灯在正常工作时,光照强度相同时的有关数据如下表

二种灯

LED灯

白炽灯

发光原理

二极管发光

钨丝高温发光

额定电压

24伏

220伏

响应时间

109

103

额定功率

12瓦

100瓦

(1)请根据以上材料说明使用LED 灯的两个优点①____ ;②____ .

(2)LED灯正常工作时的电流是____ A,每天正常工作10 小时,使用LED 灯比使用白炽灯可节约电能为____ kW•h.

上一题 下一题 0.0难度 选择题 更新时间:2015-03-25 10:05:24

答案(点此获取答案解析)

节能,额定电压低,0.5,0.88 

同类题3

   A 10-year-old boy decided to learn judo though he had lost his left arm in a car accident. The boy was doing well, so he couldn't understand why, after three months of training, the master had taught him only one move.
   “ Master,” the boy finally asked, “shouldn't I be learning more moves?"“ This is the only move you know, but this is the only move you'll ever need to know,” the teacher answered.
   Several months later, the teacher took the boy to his first competition. Surprising himself, the boy easily won his first two matches. The third match proved to be more difficult, but after some time, his opponent (对手) became impatient and charged; the boy skillfully used his one move to win the match. Still amazed by his success, the boy was now in the final.
  This time, his opponent was bigger, stronger, and more experienced. Soon after the match started, the boy seemed to lose. Thinking that the boy might get hurt, the judge called a time-out. He was going to stop the match when the teacher appeared. “ No,” the teacher said, “Let him continue.” A short time after the match carried on, his opponent made a careless mistake. At once, the boy used his move to pin (压住) him. The boy won the match and the competition.
  On the way home, the boy asked the teacher what was really in his mind. " Why could I win the competition with only one move?" The teacher answered. "First, you've mastered one of the most difficult throws in judo. Second, your opponent can only attack your left arm to win you.”
根据短文内容完成下面的表格,每空一词。

Title: One’s weakness can become his____ 
A boy had lost left arm, ____  he decided to learn judo
After three months of training, the master taught him only one move.
His first____ First three matchesHe won.
FinalHis opponent was bigger, ____  and more ____ .
At the ____ , the boy seemed to lose the match.
The judge was____  that the boy might get hurt and called a time-out.
His opponent made a mistake. The boy used his move and pinned him.
He became the ____  of the match.
____ 1. He had almost mastered one of the most difficult throws in all of judo.
 The opponent can win the match by ____  your left arm.