问题 选择题

如图所示,a、b、c、d是某电场中的4个等势面,它们是互相平行的平面,并且间距相等.下面判断中不正确的是(  )

A.这4个等势面的电势一定满足φabbccd

B.如果φa>φb,则电场方向垂直于等势面由a指向b

C.如果φa<φb,则电场方向垂直于等势面由b指向a

D.如果φa<φb,则电场强度Ea<Eb

答案

A、由图判断出电场方向垂直于等势面,由公式U=Ed可知,沿着电场线方向,相同距离电势差相同.故A正确.

    B、根据电场线总和等势面垂直,并且由电势高的等势面指向电势低的等势面可知,如果φa>φb,电场方向垂直于等势面由a向b故B正确.

    C、根据电场线总和等势面垂直,并且由电势高的等势面指向电势低的等势面可知,如果φa<φb,电场方向垂直于等势面由b指向a.故C正确.

    D、等势面是平行平面而且均匀分布,则电场线平行同向,均匀分布,匀强电场,电场强度处处相同,该电场一定是匀强电场.故D错误.

本题选不正确的,故选D

阅读理解

Word Power

Author(s): Kaplan $13,95

You'll never be at a loss for words again.Energize your vocabulary with must-know everyday words that are the essentials of a good vocabulary, engaging lessons to help you use words in text, hot words often found on tests, tips to help you figure out new words, roots, and more.

Grades: 8 & up Ages: 13 & up

Word Smart Junior

Author(s): Russell Stauffer $ 17.95

Now this is the way to add new words to your vocabulary! Word Smart Junior will make you laugh so much.You'll be amazed that you've just learned more than 120 fascinating and very useful words! Parents, teachers, and friends will marvel at your eloquence (口才)!

Grades: 3-5 Ages: 8-10

Grammar Smart Junior

Author(s): Marcia Reynolds $ 16.85

Do you quake when your teacher says, "Now it's time for grammar"? Do your verbs agree with your subjects?

Fear no more! A big Hollywood producer and a famous movie star will help you learn all those nasty (讨厌的) elements of grammar.You'll be amazed at how quickly you learn, and how much fun it can be.You'll finally know your grammar backwards and forwards and you'll never have to worry about it again.

Grades: 7-9 Ages: 12-14

Grammar Smart: An Audio Guide to Perfect Usage

Author(s): Julian Fleisher $ 12.68

The words you use say a lot about you ...but the way you put them together says even more.Your grammar makes an immediate and lasting impression on your teachers, and even your friends.So don't make the mistake of thinking that grammar is too complicated.We've created Grammar Smart to help you write and speak with clarity and confidence.

Grades: 6-8 Ages: 11-13

小题1:If a ten-year-old boy wants himself to be admired because of his speech ability, he may buy ____.

A.Word Power

B.Word Smart Junior

C.Grammar Smart Junior

D.Grammar Smart: An Audio Guide to Perfect Usage小题2:By saying "You'll finally know your grammar backwards and forwards", the writer means "_____".

A.You will be clearly familiar with grammar

B.You will know the history of grammar

C.You will know the make-up of grammar

D.You will learn about the future of grammar小题3:The four books are all about ____.

A.fiction and mysteries

B.parenting and teaching

C.literature and arts

D.language study

单项选择题 A2型题