cai nay cung hay dayDo $u_{AN} $ vuong pha $u_{MB} va u_{AB}$ lech pha $\frac{\pi }{3}$ vs $u_{AN}$ nen $u_{AB}$ lech $\frac{\pi }{6}$ vs $u_{MB}$
Sau do dung cong thuc tong hop vec to thi $ \overrightarrow{u_{AB}}-\overrightarrow{u_{MB}}=\overrightarrow{u_{AM}}$
tu do suy ra $u_{AB}$ lech pha $\frac{\pi }{6}$ so vs $u_{AM}$ hay $u_{R}$ hay dong dien trong mach va cung suy ra dk $U_{AM}=120V$
Do $P=UIcos \Phi=>I=\frac{P}{Ucos\Phi }=2A $
tinh ngay dk $R=\frac{U_{AM}}{I}=60\Omega $
Tu gian do thi $u_{AN} $ lech pha $\frac{\pi }{6}$ so vs $u_{R}$ suy ra $Z_{C}=\frac{R}{\sqrt{3} }=\frac{60}{\sqrt{3} }=20\sqrt{3}\Omega $
Khi noi tat cuon day thi $P=\frac{U^{2}R}{R^{2}+Z^{2}_{C}}=540W$