【简答题】用0℃的冰或0℃的水来冷却食物,效果较好的是______,这是因为______.
【简答题】用0℃的冰或0℃的水来冷却食物,效果较好的是__________,这是因为__________________________。
【单选题】Which of the following questions is best answered by information gained from Kohoutek?
A.
Where were comets formed?
B.
When were comets formed?
C.
Where was the solar system formed?
D.
How was the solar system formed?
【单选题】某RLC元件串联的电路中,如果感抗XL小于容抗XC,则电路的性质为( )。
【简答题】三角形三0角人度数比是1:3:3,三0角分别是______°、______°、______°;这是一0______三角形.
【简答题】用0℃的冰或0℃的水来冷却食物,效果较好的是__________,这是因为__________________________________________。
【简答题】如图所示RLC串联电路,外加工频电压U1=220V,已知电阻R=40W,电容的容抗Xc=60W,电感的感抗XL=30W,试求: (1)各元件两端的电压UR、UL、Uc; (2)电阻与电感两端的电压U2; (3)电路的有功功率P和视在功率S。