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如图1所示,L上标有“6V  3W”字样,电流表量程为0~0.6A,电压表量程为0~15V,变阻器R的最大电阻为100Ω.只闭合开关S1,滑片置于a点时,变阻器连入电路中的电阻为Ra,电流表示数为Ia;只闭合开关S2,移动滑片P,变阻器两端电压与其连入电路的电阻关系如图2所示,当滑片P置于b点时,电压表示数Ub=8V,电流表示数为Ib.已知Ra:R0=12:5,Ia:Ib=3:5(设灯丝电阻不随温度变化).求:

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Jack had an unusual experience last night. He is sharing it with his friends. Ken and May.

Ken: What were you doing, Jack What did you see

Jack: It was half past nine last night and I was getting ready for bed. I heard some strange noise outside while I was brushing my teeth. I wondered what was happening and I went to the window and looked out. To my surprise, I saw a bright yellow green light in the sky.

May: Maybe the light you saw was a UFO! Or a ghost! A few years ago, an American man saw a flying saucer while he was driving along a road. He also saw some strange yellow light. You have heard about it, haven't you

Ken: Don't be imaginative, May. Jack didn't see anything, or anybody. It wasn't a ghost. It was probably a plane, or a shooting star .Perhaps Jack just made a horrible dream!

Jack: I am very serious .I did see something. The light disappeared and then suddenly some “tiny people” were standing in the garden .There were four of them .Two of them ate some flowers in the garden .It was always stretching out its arms.

Ken: Oh, come on, Jack. I really doubt what you have said.

Jack: I am not joking! One of the people was looking at me through the window.

May: Really What did it look like Were you frightened

Jack: Its whole body was green. It had no ears and nose. Its hands were huge. Its eyes were very big and resembled eggs. It started at me and I could hardly move.

Ken: What happened then ?

Jack: I was able to move eventually. I ran and got my camera immediately.

May: And......

Jack: I didn't have a film.

May: Oh no!