问题 问答题 简答题

低压电缆主芯线截面的确定原则是什么?

答案

参考答案:(1)电缆的正常工作负荷电流应等于小于电缆允许的载流量;

(2)在正常运行时,低压电缆最远端的电压不应低于电网额定电压规定值;

(3)电缆的机械强度,应符合用电设备使用的场合要求;

(4)对距离最远,容量最大的电动机,在重载情况下应保证其起动端电压不低于额定值的75%;

(5)所选电缆截面必须能与保护装置适配,并且在短路时,应具有足够的热稳定性。

选择题
阅读理解

Hundreds of secondary schools are using a controversial reward scheme which “bribes” (贿赂)pupils with iPods and DVD players to turn up in classes and do homework.

Almost one million schoolchildren have been issued with supermarket-style reward cards which allow them to collect good-behavior “points” and cash them in for prizes.

Schools taking part in the “Vivo Miles” scheme are spending several thousand pounds a year in an attempt to cut truancy (逃学) and promote achievements. The prizes are ultimately funded by the taxpayer, through school budgets. Nearly 500 secondary schools, one in six, have decided to take part in the scheme, which is intended to replace old-style rewards such as stickers and golden stars.

But the extent of rewards being offered in schools brought a warning that a generation of children is growing up expecting to be rewarded at every stage. Many youngsters are collecting points for ordinary achievements such as remembering to bring their PE kit and wearing the correct uniform.

Under the scheme, teachers award Vivo points—worth 1 penny each—according to the school’s policy. Schools typically spend£4 to£6 on prizes per pupil each year, although some commit considerably more. Most pupils accumulate between 400 and 600 Vivos a year. Vivo Miles insists it is “pretty rare” for a pupil to accumulate enough points to buy an iPod, which requires 3,100 Vivos.

But Chris McGovern, chairman of the Campaign for Real Education, said the scheme amounted to “bribery”. “It misleads children into thinking anything which requires effort has to have a special reward,” he said. “This ‘all must have prizes’ view is damaging to children in the long-term.” The scheme amounted to an “admission of failure” by schools. He said. “It shows a school has failed to convince children education is important.”

小题1:The “Vivo Miles” scheme is aimed at ______________.

A.increasing the income of the school

B.encouraging students to perform well at school

C.inviting more students to attend the school nearby

D.encouraging parents to donate to the school小题2:The underlined word “controversial” in the first paragraph can be replaced by __________.

A.arguable

B.practical

C.strange

D.mature小题3:Those who oppose the “Vivo Miles” scheme think ______________.

A.it helps control the problem of truancy

B.it teaches children the importance of saving

C.it will mislead children about efforts and rewards

D.it’s not easy to get more than 600 Vivos a year小题4:What’s the writer’s attitude towards the scheme?

A.Supportive.

B.Opposed.

C.Unconcerned.

D.Objective.