题目内容

压气机的定温效率是压缩前气体的状态相同、压缩后气体的压力相同时，可逆定温压缩过程所消耗的功和实际压缩过程所消耗的功之比。（）

A. 对
B. 错

查看答案

搜索结果不匹配？点我反馈

更多问题

压气机按定温压缩时，气体对外放出热量，而按绝热压缩时，不向外放热，所以绝热压缩更为经济。（）

A. 对
B. 错

真空泵也可以看作为是压气机。（）

A. 对
B. 错

4 Complete the paragraph with the correct form of the words below.competentdemocraticdonationintenseintimidateprogressiverecruitsophisticatedThere are two big political parties in the United States: the Republican Party, which is traditionally the more conservative of the two, and the Democratic Party, which is said to be more (1)______. One of the most interesting and (2)_ moments in American political life is the election campaign which comes before the presidential elections. Both parties need a lot of money to pay for the campaign, for which they rely on (3) made by individuals and organizations.They also need a lot of new (4) to work on the campaign. These people are usually young, intelligent and hardworking, (5) in their jobs and not easily (6) , since they are likely to face a lot of problems which have to be resolved quickly. But they also need to be highly (7), to be able to understand what the American people have a(n) (8)__ right to ask of its government, and to communicate with them through the style and organization of the election campaign.

5 Complete the sentences with the correct form of the expressions below.be heaving within charge ofin the running forknow ... inside outrefrain fromstep outthink on one’s feettrack down1 At the end of evening, they into the quiet streets.2 It was rush hour and the streets cars, vans and buses.3 The head waiter is greeting people and showing them to their seats.4 He looked down his list of reservations, but couldn’t Lester’s name.5 If someone asked Josh a question he couldn’t answer, he would __ and come up with something.6 He’d been to the restaurant very often and _ the menu .7 The Senator was _ President next year.8 She _______ accepting the invitation not to pay the bill.