题型:名词解释 一正弦电动势的最大值为220伏,频率为50赫兹,初相位为30°,则此电动势的瞬时值表达式为()。A.e=220sin(314t+30°)B.e=220sin(314t-30°)C.e=-220sin(314t+30°)D.e=-220sin(314t-30°) 查看答案