【简答题】根据短文内容,从下面方框中选择适当的词组填空,使短文内容完整正确 growing up feels worried about put on to wait for takes good care of Only Mother Love is true love. It gives everybody everything all his life. When you ar...
【简答题】如图(a)所示为一个简单的产生锯齿波电压的电路原理图。已知U s =12V,R 1 =6kΩ,R 2 =20Ω,C=0.4uF。开关S打开时.电容被充电,电容电压u c 上升到6V时,开关S闭合,电容对电阻R 2 放电。电容电压u c 下降到接近为零时,S又打开,电容C又被充电,u c 上升到6V时,S又闭合,如此周期性进行。试分析电容电压u c 和电阻R 2 的电压u R 2 ,并画出它们随时间...
【简答题】根据短文内容,从下面方框中选择适当的短语填空,使短文内容完整正确。 Since last winter, the smog has occurred a lot of times in China. It has done great harm to our daily life. Many traffic accidents happened just 小题1: the heavy smog w...