问题 选择题

在如图所示电路中,电源电动势为12V,内电阻1Ω。闭合S后,调整R的阻值,使电压表的示数增大ΔU=2V。在这一过程中 ( )

A.通过R1的电流增大,增量小于ΔU/R1

B.R2两端的电压减少2V

C.通过R2的电流减少,减少量小于ΔU/R2

D.路端电压增大2V

答案

答案:C

由于调整R的增大,总电流减小,使电压表示数增加了2V,由于电路总电流的减小,则外电压比原来变大,UR2=U-UV,则△UR2<2V=△U,C正确。

阅读理解

Tom saw an advertisement in a newspaper for a beautiful bicycle. It cost 55 pounds. So he went to the shop and asked to see one of the wonderful bicycles.

The owner of the shop was harpy to show one to Tom. Tom examined(检查)it carefully, and turned to the owner and said, "There isn’t a lamp on this bicycle. hut there was one on the bicycle in your advertisement."

"Yes, Sir, "answered the man." But the lamp isn’t included(包含)in the price of bicycle."

"Not included in the price of bicycle?" Tom said angrily. "But that’s not honest. If the lamp is in the advertisement, it should be included in the price.”“Well, Sir,” answered the shop owner coldly. "There is also a girl on the bicycle in the advertisement. but we cannot give you a girl with the bicycle, either."

小题1:In the advertisement, there was a ______ and a ______ on the bicycle.

A.lamp; man

B.picture; lamp

C.lamp; girl

D.newspaper; shop owner小题2: After he read the advertisement, Tom decided to ______.

A.see and buy the lamp

B.examine the bicycle

C.see and buy the bike

D.ask the shop owner小题3:Tom ______ after he looked at the bike carefully.

A.returned the bike to the shop owner

B.didn’t find a lamp on the bicycle

C.showed the bike to the shop owner

D.bought the bicycle at once小题4: Tom thought it was ______ for the shop owner to sell the bike without a lamp while there was one in the advertisement.

A.necessary

B.good

C.right

D.wrong小题5: The text gives us a lesson that ______.

A.sometimes we can’t completely (完全地) believe an advertisement.

B.we must read the newspaper carefully

C.The price of something is often changed

D.we should examine bicycles carefully before we buy them

问答题