问题 实验题

某物理“科技制作”小组装配一台小直流电动机,其额定电压5V,额定电流0.5A,线圈绕阻小于1。为了进一步研究其在一定电压范围内,输出功率与输入电压的关系,需要进一步做实验,请你帮助该小组完成该项工作。已知学校实验室提供的器材有:

直流电源E,电压6V,内阻不计;

小直流电动机M;

电压表V1,量程0~0.6V,内阻约3k

电压表V2,量程0~6V,内阻约15k

电流表A1,量程0~0.6A,内阻约1

电流表A2,量程0~3A,内阻约0.5

滑动变阻器R,0~10,2A;

电键S一只,导线若干。

(1)首先要比较精确测量电动机的线圈绕阻。根据合理的电路进行测量时,要控制电动机不转动,调节滑动变阻器,使电压表和电流表有合适的示数,电压表应该选        。若电压表的示数为0.1V,电流表的示数为0.2A,则内阻        ,这个结果比真实值偏         (选填“大”或“小”)。

(2)在图方框中画出研究电动机的输出功率与输入电压的关系的实验电路图。(标明所选器材的符号)

(3)当电压表的示数为4.5V时,电流表示数如图所示,此时电动机的输出功率是     W。

答案

①V1  0.5 小(3分) ②(4分)③1.72(4分)

(1)让滑动变阻器处于最大阻值处,电路中的电动机不转圈时最大电压为,所以选用V1  ,根据欧姆定律得电动机内阻为r=0.5,因为电流表测量的是电压表和电动机的总电流,所以电流测量值比真实值大,故测得的内阻偏小,

(2)采用分压法,电流表的外接法。

(3)根据1分度盘读法可得电流为0.40A,根据公式 .

多项选择题
阅读理解

At times we all get angry when we are driving. It might be because we are stuck in a traffic jam or stuck behind a very slow driver. It might be because we think another driver has done something very stupid and dangerous. Whatever the reason, it seems that getting angry in a car is something which happens more and more often and there is now a special term for it “road rage”. Some experts even think that road rage is a kind of mental illness! How can we recognize this “illness” of road rage?

There are two kinds of road rage: aggressive driving and aggressive reactions to the way other people are driving. Aggressive driving can take different forms:

●Driving much faster than the speed limit.

●Increasing your speed very quickly.

●Driving very close behind the car in front and sounding the horn or flashing the headlights.

●Changing lanes very suddenly and blocking another car.

●Moving into a parking space where another car is trying to park.

There are also different reactions to the way other people are driving. These include:

●Making rude signs at people.

●Shouting at people and threatening them.

●Deliberately driving into another person’s car.

●Hitting somebody.

●Using a weapon such as a baseball bat, or even a gun or a knife.

Road rage is certainly not a joke. There have been incidents of road rage which have led to serious injuries and even murder.

Experts think that one reason for road rage is that films show a lot of examples of fast and aggressive driving such as car chases where this kind of driving seems to be positive.

Experts also think that the punishments for dangerous driving are not serious enough.

Experience shows that driving problems can be controlled, but it takes a long time. In the UK in the last 30 years, the police have been quite successful in reducing the number of people who drink and drive. They are now working to stop people using mobile phones when they are driving. Let’s hope they can have the same success with the road rage.

小题1:Which of the following statements does NOT describe aggressive     driving?

A.Driving much faster than the speed limit.

B.Drinking and driving

C.Moving into a parking space where another car is trying to park.

D.Changing lanes very suddenly and blocking another car.小题2:Road rage happens possibly because______.

A.the drivers are drunk

B.it won’t cause serious injuries or death

C.we’re in a fast-changing society

D.the punishments are not serious enough小题3:What’s the tone(语气)of the last paragraph?

A.Sad

B.Cold

C. Optimistic

D.Exciting