Ur^2 + Uc^2 = Urc^2
Ur^2 + Uc^2 = 150^2 (1)
(UL - Uc)^2 + Ur^2 = U^2
(150^2 - Uc)^2 + Ur^2 = 150^2 (2)
解得：
Uc = 75V
Ur = 75 √3 V
I = Ur / R
= 3 √3 A
选b么，好像是这么回事
