问题 问答题 简答题

三相电能表测量机构各部件的作用是什么?

答案

参考答案:

单、三相电能表测量机构各部件的作用:

(1)驱动元件的作用是将交变的电压和电流转变为穿过转盘的交变磁通,与其在转盘中感应的电流相互作用,产生驱动力矩,使转盘转动。

(2)转动元件的作用是在驱动元件建立的交变磁场作用下连续转动。

(3)轴承的作用是支撑转动元件的全部重量,减少转动时的摩擦。其质量好坏直接影响电能表的准确度和使用寿命。

(4)制动元件的作用是利用转动着的转盘切割永久磁铁产生的磁通,在转盘中所产生的感应电流相互作用形成制动力矩,使转盘的转动速度和被测功率成正比变化。

(5)计度器的作用是累计转盘的转数,显示测定的电能。

阅读理解

阅读理解。

     In most parts of the world, many students help their schools make less pollution (污染). They join

"environment clubs (环境俱乐部)". In an environment club, people work together to make our

environment clean.

     Here are some things students often do.

     No-garbage (垃圾) lunches. How much do you throw away after lunch? Environment clubs ask

students to bring their lunches in bags that can be used again. Every week they will choose the classes

that make the least garbage and report them to the whole school!

     No-car day. On a no-car day, nobody comes to school in a car-not the students and not the

teachers! Cars give pollution to our air, so remember:

     Walk, jump, bike or run.

     Use your legs! It's lots of fun!

     Turn off the water! Did you know that some toilets can waste(浪费) twenty to forty m3 of water an

hour? In a year, that would fill a small river! In environment clubs, students mend those broken toilets.

     We love our environment. Let's work together to make it clean.

1. Environment clubs ask students         .

A. to run to school every day            

B. to take exercise every day

C. not to forget to take cars              

D. not to throw away lunch bags

2. From the passage we know the students usually have lunch         .

A. at school          

B. in shops        

C. in clubs        

D. at home

3. On a no-car day,          will take a car to school.

A. both students and teachers              

B. only students

C. neither students nor teachers            

D. only teachers

4. After students mend toilets, they save          .

A. a smaller river      

B. a club      

C. a lot of water      

D. a toilet

5. The writer wrote the passage to ask students to          .

A. clean schools    

B. make less pollution      

C. join clubs      

D. help teachers

单项选择题