问题
填空题
我国交流电的周期为______s，频率为______Hz．
答案
我国用的交流电的周期为0.02s，根据周期和频率互为倒数的关系可知，此时的频率为f=
=50Hz．1 T
故答案为：0.02，50．
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我国交流电的周期为______s，频率为______Hz．
我国用的交流电的周期为0.02s，根据周期和频率互为倒数的关系可知，此时的频率为f=
=50Hz．1 T
故答案为：0.02，50．
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| Whatever misfortune you face, just hold up your head and face it with a smile! I got to know this from a musical soul. The other day I was feeling quite 1 , having just been laid off from my job. With so many 2 to pay, I was wondering what was going to happen to my family. I got off the bus when I heard piano music and singing rising above the noise of the 3 . I walked a bit slower, trying to find out where it was coming from. Through the 4 I saw a young lady sitting at a piano with a box next to her. She was singing songs about love and her sweet voice 5 me a bit. Then I stood there watching her playing, thinking that it must take 6 to perform on her own in front of hundreds of people she didn't know. She might have felt my 7 for she occasionally looked in my direction. By now I was telling myself that I could at least tell her how good she sounded. I walked 8 and put some money in her box and she expressed her thanks with a smile on her face. I asked her 9 , "Why are you playing the piano in the middle of this crowded place?" She explained to me that she sees so many 10 people in the world that she is trying to relieve the pain by 11 motivational music. Instead of continuing my way home, I said to her, "I have been going through a 12 time lately, but you've made me 13 again." "I'm happy that I could be 14 to you," she replied. "Why are you so sad?" I told her my story and said, "I'm not so 15 about what to do…." "You see, here's the 16 ," she responded. "When you were walking, your head was down." She looked me in the eyes and went on, "Don't look defeated, because 17 comes in different ways and if your head is down you might never see it. You should 18 more …lift your head up." I was really 19 by what she said! I did hold my head up and soon got through the difficult time. So 20 in trouble, just face it bravely and you are sure to overcome your difficulty sooner or later. | ||||
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