Nguon coi la dk chia thanh 2 la nguon mot chieu $U_{1}=100V$ va xoay chieu $u_{2}=100cos(100\pi t+\frac{\pi}{4})$
Nguon mot chieu tao cong suat :
$P_{1}=0 W$ (do mach co tu nen khong co dong chay qua)
Nguon xoay chieu tao cong suat lon nhat la:
$P_{2}max=\frac{U^2_{2}}{2R}=25 W$
Cong suat lon nhat la:
$Pmax=P_{2}max=25 W$
Vay ta chon dap an $D$