题干

有一个额定电压为2.8V,功率约为0.8W的小灯泡,现要用伏安法描绘这个灯泡的如图1I﹣U图线,有下列器材供选用:

A.电压表(0~3V,内阻6kΩ)

B.电压表(0~15V,内阻30kΩ)

C.电流表(0~3A,内阻0.1Ω)

D.电流表(0~0.6A,内阻0.5Ω)

E.滑动变阻器(10Ω,2A)

F.滑动变阻器(200Ω,0.5A)

G.蓄电池(电动势6V,内阻不计)

①用如图2所示的电路进行测量,电流表应选用____.滑动变阻器应选用____.(用序号字母表示)

②通过实验测得此灯泡的伏安特性曲线如图1所示.由图线可求得此灯泡在正常工作时的电流为____ A.

③若将此灯泡与电动势6V、内阻不计的电源相连,要使灯泡正常发光,需串联一个阻值为____Ω的电阻.

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D,E,0.28,11.4

同类题4

阅读短文,下列问题

 B

    Did you know that each day one person in the US throws away 4.4 pounds of rubbish? Almost every month, we throw away our own rubbish in packaging alone. Packaging (including boxes, bags, etc.) comes to our homes with the things we have bought. Several weeks ago, the TV news said that in a city in Italy tons of rubbish were piled up in the streets, and the smell was rather terrible. What can we do to help? We should get to know the following Rs.

Reduce  

    To reduce means to make less rubbish. That is one of the first things we all should do for the environment. Reduce your rubbish by doing things like packing your lunch in reusable containers (可再利用的容器), taking smaller portions (份) at dinner so you don't waste food when you have had enough, writing on both sides of paper, and using less water when taking a shower.

Reuse   

    To reuse is to use things again. Think about the bags you get from the store. They can be reused to carry your lunch, to hold your rubbish, or to collect used cans. You can even take them back to the store the next time to carry your things instead of getting a new bag!

Recycle(回收利用)  

    Recycling is an important part of keeping our planet clean and green. It can also save energy. Be sure that you don't throw things in the rubbish that can be recycled to make something else. Paper, plastic, cans and bottles can all be recycled, but food, electrical waste and mobile phones can't. When you are not sure whether something can be recycled, go to your parents and teachers for advice.

    Follow the three Rs, and every one of us can do something to save the earth. It is also the best way to save ourselves.