2.正弦电流、电压的有效值 设i(1)= L cos((Og) def1 cT i(t)dt /m cos(at+o )dt f cos (t+p)dt=J T 1+cos 2(at todt= 2 2 2 =0.7071 Tm2√2 =√2I i(t=Im cos(at +)=v2I cos(at+P)2. 正弦电流、电压的有效值 设 i(t)=Imcos(w t+  ) I t t T I T cos ( )d 1 0 2 2 =  m w + t t T t t t T T T 2 1 2 1 d 2 1 cos 2( ) cos ( ) d 0 0 0 2 = = + + + =   w   w  I I I T I I T I 2 0.707 2 2 1 m m 2 m m =  =  = = ( ) cos( ) 2 cos( ) i t = I m wt + = I wt +  = T i t t T I 0 2 def ( )d 1