合理选用电动机功率是电动机节电的有效措施。一般情况下,电动机负载率小于()时,应考虑 发布时间:2019-09-25 10:20 │ 来源:www.tikuol.com 题型:单项选择题 问题: 合理选用电动机功率是电动机节电的有效措施。一般情况下,电动机负载率小于()时,应考虑更换容量合理的电动机。A.40%;B.50%;C.60%;D.70%
题型:单项选择题 在点电荷Q的电场中,一个α粒子(氦的原子核)通过时的轨迹如图实线所示,a、b为两个等势面,则下列判断中正确的是( )A.Q可能为正电荷,也可能为负电荷B.粒子从b到a的过程中电场力做正功C.α粒子经过两等势面的动能Eka>EkbD.α粒子在两等势面上的电势能Epa>Epb 查看答案
题型:单项选择题 — Why didn't you buy the book?— I _____, but I didn't have the money. [ ]A. would have B. bought C. would like to D. had bought 查看答案