问题 选择题

如图所示,三个电压表用满偏电流相同的电流表改装而成,已知电压表V1的示数为8v,电压表V3的示数为5V,则关于电压表V2的示数,下列判定中正确的是(  )

A.电压表V2的示数必为3V

B.电压表V2的示数必为5V

C.若三个电压表量程相同,则电压表V2的示数必为3V

D.即使三个电压表量程相同,电压表V2的示数也可能不等于3V

答案

A、B,电压表V2与电阻串联,串联的总电压等于V3的示数5V,所以V2的示数必定小于5V,由于三个电压表量程关系未知,无法确定其示数.故AB错误.

C、D,三个电压表用满偏电流相同的电流表改装而成,满偏电流相等,若电压量程相同,则三个电压表的内阻相等,设为R.

通过电压表V2的电流为I2=I1-I3=

U1
R
-
U3
R
=
U1-U3
R
=
3
R

电压表V2的示数为U2=I2R=3V.故C正确,D错误.

故选C

阅读理解

On August 15, 2011,the Ministry Publish Security (公安部) started a campaign (活动) to educate drivers about the dangers of driving after drinking.

As a part of the campaign, police officers watched bars, restaurants and KTVs in Beijing, Shanghai, Liaoning, Jiangsu, Zhejiang, Hubei and Guangdong. It ended up on December 30. But it told the drivers the meaning of the new traffic laws and the dangers of drinking.

In Beijing, some restaurants put up notices and told drivers about their responsibility. “Usually if a group of guests come by car, the driver won’t drink. If he does, we will remind him,” said a waitress from Dongfang Restaurant in Beijing. Fewer drivers are drinking alcohol nowadays, since many know about the campaign.

Wang Lankun, a traffic policeman in Beijing said, “Some drivers think a glass of beer is not a problem. But a blood test will show that their blood-alcohol level is more than 20mg for each 100ml of blood, that is enough to affect their driving.”

During the campaign, drivers who have a blood-alcohol level of over 20mg for each 100ml of blood will get a fine of 500 yuan. Also, they will not be allowed to drive for three months.

In fact, there are strict laws to punish drunk driving in many other countries. For example, in the USA, if someone has a blood-alcohol level of over 80mg for each 100ml of blood, he will be sent to prison for one year. But in Britain, he will be fined 5,000 pounds and banned (禁止)from driving for 12 months, also he will be sent to prison for 6 months. In Germany, if a driver has a blood-alcohol level of over 60mg for each 100ml of blood, he won’t be allowed to drive until he passes a new driving test.

小题1:How long did the campaign last?

A.For about half a year.

B.For about four and a half months.

C.For about 12 months.

D.For about three months.小题2:The police officers watched many places except ___________.

A.restaurants

B.KTVs

C.schools

D.bars小题3:If a driver drinks a glass of beer before driving in China,_________

A.it won’t affect his driving.

B.he will take a new driving test and get a driver’s license.

C.he won’t be allowed to drive for three months.

D.his blood-alcohol level will be over 60mg for each 100ml of blood.小题4:If a driver has a blood-alcohol level of over 80mg for each 100ml of blood in Germany,

which punishment will he accept?

A.One year in prison.

B.Banned until he passes a new driving test.

C.A 12-month ban from the roads.

D.A fine of 5000 pounds.小题5:From the text, we know_________.

A.The waitress in the restaurant can remind the driver not to drink

B.More and more drivers are drinking alcohol nowadays

C.The Ministry Publish Security began this campaign to punish the drivers

D.All drivers must pass a new driving test if they drive after drinking

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