【多选题】如图所示,理想变压器原线圈接交流电源,副线圈接电阻箱R、电容器C和电感器L,下列说法正确的是
A.
仅当电阻箱R的阻值变大时,变压器输入功率减小
B.
仅当电容器C的正对面积增大时,通过它的电流减小
C.
仅当交流电源的频率增大时,通过三个元件的电流都增大
D.
仅当在电感线圈L中插入铁芯时,通过它的电流将减小
【简答题】将L=20mH的电感元件,接在频率f=50Hz的交流电源上,则其感抗大小为()Ω。
【判断题】With credit cards, you can collect points and with points you can get money back or free gifts, so you will come again very soon.
【单选题】《地下铁道设计规范》规定:正线的最大坡度宜采用( )
【判断题】When you pack for a four-day trip, take a big suitcase or a heavy backpack with you so you can save money because you can use public transport with ease.
【单选题】《地下铁道设计规范》规定:正线的最大坡度宜采用( )。
【简答题】You can use any printer if you handle it with care. You can use the one you like. You can use whichever printer ________.
【单选题】《地下铁道设计规范》规定,正线的最大坡度宜采用()。
【简答题】You can stay with us. You can play football with Sam. You can _______stay with us _________play football with Sam.