问题
选择题
加在某台电动机上的电压是U，电动机消耗的电功率为P，电动机线圈的电阻为R，则电动机线圈上消耗的热功率为
A．
B．
C．
D．
答案
答案：B
本题考查非纯电阻用电器的功率。电流
，线圈的热功率
，选B。
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加在某台电动机上的电压是U，电动机消耗的电功率为P，电动机线圈的电阻为R，则电动机线圈上消耗的热功率为
A．
B．
C．
D．
答案：B
本题考查非纯电阻用电器的功率。电流，线圈的热功率，选B。
My daughter performed（表演） on behalf（代表） of her class in the annual（每年的） school concert today. She played so that I could not help cheering her. The very reminded me of her experiences of piano practicing. When she was five, we gave her a piano as a birthday present. With great , she began learning it. However, when she was no longer , she became sick of （厌烦）it. , it is a tough job to learn the piano, not to mention the daily routine（常规）of . When her first teacher left, my friend me to an American teacher whose way of teaching was completely American. After practicing, she would give my daughter some comments（评论）, and then point out what should be . Every time she came, beginning the lesson right away, she would first play some . She said, “To learn the piano, you should learn not only the of playing, but more importantly, to the music and love it.” After some time, my daughter became fond of her lessons. Sometimes she would like to a little bit when her skill had reached a certain level. Surprisingly, my daughter said to me one day, “Mom, I was that you didn’t give up my piano lessons. Learning it is like climbing a mountain. You’ll feel when you are on the way. When you look from where you are, you will realize that you have been making . But if you , you’ll never take one more step.” That was the very thing I wanted to teach her.
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