问题
多项选择题
下列关于直接接于电网的同步电动机的运行的性能的表述中，哪些是正确的？（）
A.不可以超前的功率因数输出无功功率
B.同步电动机无功无偿的能力与电动机的负荷率、励磁电流及额定功率因数有关
C.在电网频率恒定的情况下，电动机的转速是恒定的
D.同步电动机的力矩与电源电压的二次方成正比
答案
参考答案：B, C
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下列关于直接接于电网的同步电动机的运行的性能的表述中，哪些是正确的？（）
A.不可以超前的功率因数输出无功功率
B.同步电动机无功无偿的能力与电动机的负荷率、励磁电流及额定功率因数有关
C.在电网频率恒定的情况下，电动机的转速是恒定的
D.同步电动机的力矩与电源电压的二次方成正比
参考答案：B, C
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| As a music teacher, I have always known that music touches the soul. It can __1__ all kinds of barriers to reach students in a very special way. It can be the __2__ for each child to find their light. I would like to __3__ a story about it. For a few years I was __4__ with the opportunity to teach disabled students. One of my most __5__ students was a fiveyearold girl called Vanessa, who had difficulty walking, and could not speak. We __6__ sat on the floor for our music lessons and Vanessa liked to __7__ on my lap(大腿). One of her favorite songs was John the Rabbit. It was a call and response song where I sang the call and the students __8__ twice while singing the repeating phrase," Oh, yes !" Vanessa liked to __9__ her hands together with mine and clap with me. We probably performed that song during every class, Vanessa and I clapping together. But she__10__said or sang a word. One day, when the song was finished, Vanessa turned around,__11__ me in the eye, clapped her tiny hands twice and said the words "Oh, yes!" I opened my mouth in __12__ and for that moment I was the one who could not speak. When my heart __13__ started beating again, I looked over at the assistant teacher to find her also __14___. Through music, we had made an awesome connection. Several years later, I met Vanessa on the street in town. She waved with a big __15__ on her face and then clapped her hands twice, imitating the song we had __16__ so many times in our music class. The little girl, __17__ her connection with music, left an impression on me that will last forever. Every child has the __18__ to learn and grow. It is up to us to __19__ the way to reach each and every one of our students. We all must find each child's __20__. | ||||
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