问题 选择题

在研究微型电动机的性能时,应用如图所示的实验电路.当调节滑动变阻器R并控制电动机停止转动时,电流表和电压表的示数分别为0.50A和2.0V.重新调节R并使电动机恢复正常运转,此时电流表和电压表的示数分别为2.0A和24.0V.则这台电动机正常运转时输出功率为(  )

A.47W

B.44W

C.32W

D.48W

答案

电动机的电阻R=

U
I
=
2
0.5
=4Ω;

电动机的总功率P=U1I1=24V×2A=48W;

克服自身电阻的功率PR=I12R=(2A)2×4Ω=16W;

电动机正常运转时的输出功率是P输出=P-PR=48W-16W=32W.

故选C.

阅读理解

I don’t really care how many claws the animal in a comic book (漫画书) has. I’m not overly concerned whether the bird is colored green or grey. In fact I don’t think comic book “collector” really applies to me at all. I’m probably more of a comic book “appreciator”. My interest has always been in what can be accomplished with the medium of “visual story - telling”. In the respect, comic books are the best thing going. And there are some great comics out there.

I’m not sure exactly where this interest of mine came from. I do know that as a child, comic books allowed me to improve my reading – skills. The Mighty Thor made me develop an interest in Norse legends; Challengers of the Unknown got me interested in science fiction. The combination of words and pictures was a perfect springboard (起点) for my childhood imagination.

So just how does one learn to appreciate comic book art? There is a classic example. Writer Scott Macloud was philosophical (达观的) about what makes a comic book stand out in his best – selling book Understanding Comics. The book, first published in 1994, has been translated into 13 languages and is practically useful for students studying graphic illustration (图示说明).

On the Internet there are some cool comic book sites to be found. More than a few are mainly about superheroes and the like. But there are some choice sites that I would describe as “literary (文学的),” in that you can find some great resources that discuss the comic book as an art form. Among them there is a great article and interview at www.rcharvey.com discussing the influence of several artists and writers in the field.

Check it out. Spend two dollars on a comic book and read it with your children. You may find yourself enjoying what you see and read. You may even find yourself wanting more.

And wanting to read more is a good thing!

53.According to Para. 1 the author is concerned about          .

A.the color of the characters in a comic book

B.how many comic books he has collected

C.what he can learn from a visual story

D.whether a story is true to life

54.What do we know about Scott Macloud’s best – selling book?

A.There are many classic examples if comic books in it.

B.It is helpful 1 for students studying science fiction.

C.It suggests what good comic books are like.

D.It is mainly intended for parents.

55.In the passage, the author encourages people to         .

A.follow the example of superheroes from comic books

B.join in the discussion at www.rcharvey.com

C.consider comic books to be literary.

D.buy and read more comic books

56.What is the best title for the passage?

A.Children’s favorite books

B.Well – known comic books

C.Comic books – cooler than you think

D.How to become a good comic book writer

单项选择题