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简述用户选择电极功率的原则？

答案

参考答案：

以50吨电炉为例，炼每吨钢占变压器容量350KVA以下为普通电炉，占350—600KVA为高功率电炉，占600KVA以上为超高功率电炉。依据电炉的功率选用电极的功率。

完形填空

Dr. Kate: Radio _小题1:  (change) a lot since we were young. It used _ 小题2: be the major source of' fun for the family.

Bob:      Nowadays when you turn on the radio, you either hear music, a talk show小题3: news.

Dr. Kate: 小题4:  (Fortunate), you can choose the kind of music you want to hear.

Bob:      Yes, and there is a lot of points of view when you listen to talk shows. I usually enjoy  小题5:  (listen) to them. I particularly like it w-hen a caller disagrees with the talk show host. I like to hear how he will defend his ideas.

Dr. Kate: Some talk show hosts are very rude to those  小题6: have opposing ideas. I really find that terrible.

Bob:     It seems that people only listen to the radi0  小题7:  they are driving in their car ，

Dr. Kate: That is true for me. but I know that my husband listens to it while he is working  小题8: home.

Bob:   Now that f think about it, I realize that a lot of stores have the radi0  小题9:  (play).

Dr. Kate: It's still a usefully and pleasant form of  小题10: (communicate).
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选择题

如图所示，质量相同的两木块M、N，中间固定一轻弹簧，M放在粗糙的水平面上，N放在光滑的水平面上，用力将两物体靠近使弹簧压缩，此时弹簧的弹力大于M所受到的最大静摩擦力，当松手后两物体被弹开的过程中，不计空气阻力，则对两木块，有 （   ）

A．动量守恒、机械能守恒

B．动量守恒、机械能不守恒

C．动量、机械能都不守恒

D．加速度大小任意时刻相等
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