Câu 1:
\(P'=U'I=198\left(\dfrac{60}{220}\right)=54\)W
Câu 2:
Trong mạch song song:
\(\left[{}\begin{matrix}\left\{{}\begin{matrix}R=\dfrac{R1.R2}{R1+R2}\\\dfrac{1}{R}=\dfrac{1}{R1}+\dfrac{1}{R2}+...+\dfrac{1}{Rn}\end{matrix}\right.\\U=U1=U2=...=Un\\I=I1+I2+...+In\end{matrix}\right.\)