例 已知:R=3g L e(t)=20sin(ot+30°) cT"。Hac(0-)=3 (0_)=0A 求:i(04)u(04)iR(0+),L(0+) 解:由 R(0+)=3 c(0+)=3 i(0+)=0 可求出(0)=7 iR(0+)=1A e(0)=10V 0+) 1A已知: R=3 i A u V e t t L C (0 ) 0 (0 ) 3 ( ) 20sin( 30 ) = = = +  − −  求： (0 ) (0 ) (0 ) (0 ) C + L + R + uR + i ，u ，i ， 解：由 uL (0+ ) = 7V uR (0+ ) = 3V i A i A C R (0 ) 1 (0 ) 1 = − = + + (0 ) 0 (0 ) 3 = = + + L C i u V e(0)=10V R L C e(t) + - u c i L i C u o 例 ： 可求出