已知正弦电压u=220sin（ωt-90°），则t=0时，该电压瞬时（）

A.220

B.110

C.0

D.155.6

A.30

B.220

C.50

D.100π

A.相位

B.频率

C.初相

D.角频率

A.30

B.220

C.50

D.100π

A.50

B.6.28

C.1

D.2

A.相位

B.频率

C.初相

D.角频率

A.220V

B.10V

C.0V

D.155.9V

A.220V

B.110V

C.0V

D.155.6V

A.u=220sin(50t+60°)V

B.u=220sin(314t+60°)V

C.u=311sin(50t+60°)V

D.u=311sin(314t+60°)V

A.u=110sin（50πt+30°）∨

B.u=110sin（50πt-30°）V

C.u=220sin（100πt+30"）V

D.u=220sin（100πt-30°）V