题干

下列说法中正确的是(   )

A:公式I=U/R表示:在导体电阻一定时,通过导体的电流跟导体两端的电压成正比

B:公式R=U/I表示:导体的电阻与其两端的电压成正比,与通过它的电流成反比

C:一个用电器工作时有电流通过,则该用电器两端电压一定不为零

D:绝缘体一定有电阻,导体一定没有电阻

上一题 下一题 0.0难度 选择题 更新时间:2020-02-11 07:08:37

答案(点此获取答案解析)

A,C

同类题4

根据句短文理解,完成下列各题。

       A group of people asked this question to a group 4-to-8-year-old children. “What does love mean?” The answers were surprising. The children would answer like they did below.

  “When my grandmother hurt her knees (膝盖), she couldn't bent (弯腰) over and paint her toenails (脚指甲) any more. So my grandfather does it for her all the time, even when his hands hurt too. That's love.”

                                                                                                                                                                   Rebecca–age 8

 “Love is when someone hurts you. And you get so mad but you don't shout at them because you know it would hurt her feelings.”

                                                                                                                                                                  Samantha–age 6

  “Love is what makes you smile when you're tired.”

                                                                                                                                                                  Terri–age 4

 “I let my big sister pick on (捉弄) me because my mum says she only picks on me because she loves me. So I pick on my baby sister because I love her.”

                                                                                                                                                                  Bethany–age 4

  “I know my older sister loves me because she gives me all her old clothes and has to go out and buy new clothes.”

                                                                                                                                                                  Lauren–age 4

   “Love is when Mommy gives Daddy the best piece of chicken.”

                                                                                                                                                                   Elaine–age 5

   “My mommy loves me more than anybody. You don’t see anyone else kissing me to sleep at night.”

                                                                                                                                                                  Clear–age 5

   “You really shouldn't say ‘I love you’ unless you mean it. But if you mean it, you should say it a lot. People forget.”

                                                                                                                                                                  Jessica–age 8