若电流i=i1+i2,且i1=10sinwtA,,i2=10sinwtA,则i的有效值为()
A.20A
B.20/2A
C.10A
D.10/2A
参考答案:B
—Is this your key?
—______. [ ]
A. Yes, it is
B. No, it is
C. Yes, it isn't
使用计算机的次数少或使用的时间短,就能延长使用寿命