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[单选题]
已知工频正弦电压有效值和初始值为380V,则该电压的瞬时值表达式为()。
A.u=380sin314tV
B.u=537sin(314t+45°)v
C.u=380sin(314t+90°)V
D.u=380sin(314t+45°)V
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A.u=380sin314tV
B.u=537sin(314t+45°)v
C.u=380sin(314t+90°)V
D.u=380sin(314t+45°)V
A.u=380sin314tV
B.u=537sin(314t+45°)V
C.u=380sin(314t+90°)V
D.u=380sin(314t+45°)V
A.
C.
某正弦电压有效值为380V,频率为50Hz,计时始数值等于380V,其瞬时值表达式为
A.u=380sin50πtV
B.u=220sin(100πt+45°)V
C.u=380sin(100πt+90°)V
D.u=220sin(628t+90°)V
已知正弦电压Um=210V,φu=-30°,正弦电流Im=10A,电流超前电压60°相位角,则电压电流瞬时值解析式u和i可表示为______。
A.μ=10sin(5t+30°)
B.μ=102sin(5t+30°)
C.μ=10sin(31.4t+30°)
D.μ=102sin(31.4+30°)