题干

如图所示,电源电压保持不变,闭合开关S,当滑动变阻器的滑片P从最上端向下端滑动时,四个电表的示数都发生了变化,电表的示数分别用I、U1、U2、U3表示,电表示数变化量的大小分别用△I、△U1、△U2和△U3表示,电阻R1、R2、R3(R2>R1+R3)消耗的电功率分别用P1、P2、P3表示,下列判断不正确的是(   )

A:U1I 不变, U1I 不变

B:U2I 变大, U2I 不变

C:U3I 变大, U3I 变大

D:滑动变阻器的滑片向下滑动时,P1变小,P2先变大后变小,P3变小

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答案(点此获取答案解析)

C

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    In the middle of a beautiful day, I was feeling lost, as if the world was crashing on me. didn't know which way to go, except to head out to the countryside. I went to the spot where I used to take my kids-when I still had kids. Now they had  1and were leaving.

I was sitting alone in my car when I saw a man in his seventies, whose problem appeared bigger than mine. He stood near the edge of the road,2a kite spindle(风筝线锭) in his hands. Apparently, lost in thought, he stared skyward. I 3my neck to see how successful he had been in 4 the clouds. Following his string with my eyes, I almost lost5 of the other end. Finally, the kite rested on what seemed to be the highest branch of the 6tree in the park.  Obviously,  that was his grandson's kite!  The kite was a replica (复制品) of a beautiful bald eagle, and its wings spread 70pen. Grandpa had only one 8to his problem: cut the string.

"You wanted it to fly as high as it could. Bill. didn't you?" "Yes, Grandpa,9 wanted to keep it forever. " "There just comes a time when the only thing you can do is to cut the string and let it go. Perhaps by doing that, when it flies very high like real eagles do, it will come back to us. " Grandpa said.

    I 10 how the old man cut the string to let fly the kite. As the two walked away, looked to the 11. There I saw my answer, too. Today I have to cut the final strings that kept my two boys 12my reach. Though I want to keep them forever, I have taught them to fly like an eagle. Maybe by doing this, when it's time to soar like real eagles do. one day they would come back to me.