4.3电路定律的相量形式 例 1,=L,=10A,U=100V和i同相 求、R、X和X -1X 设i=10∠0°Ai,=10∠90°A(原因：0R=i,joC)i=10√2∠45A 0=100∠45VUR=VU2+U=1002V0.=100∠135V☑R=1002∠0V 等边直角△ 1=14.1AR= R=14.12例 1 2 I I U = = = 10A, 100V u和i同相 求I、R、XC和XL。 R L jXUL C − jX 1I I UR 2 I U 0 I =  10 2 45 A 0 U =  100 45 V 0 2 2 100 2V UL =  100 135 V U U U R L  = + = 等边直角 2 14.1 UR R I = =  1 14.1 C R X U I L L 7.07 = =  U X I = =  0 UR =  100 2 0 V UL 2 I 1 I I U UR 0 2 设I =  10 0 A 1 0 1 10 A ) 90 ( = / R I U j =  原因： I C I =14.1A 4.3 电路定律的相量形式