Đáp án:
a. \({R_2} = 6\Omega ,P = 9W\)
b. Đ(4,5V,6,75W)
Giải thích các bước giải:
\(\begin{array}{l}
a.\\
{U_1} = U - {U_2} = 12 - 4,5 = 7,5V\\
I = \frac{{{U_1}}}{{{R_1}}} = \frac{{7,5}}{{10}} = 0,75A\\
{R_2} = \frac{{{U_2}}}{I} = \frac{{4,5}}{{0,75}} = 6\Omega \\
P = UI = 12.0,75 = 9W\\
b.\\
R = {R_1} + \frac{{{R_2}{R_D}}}{{{R_2} + {R_D}}} = 10 + \frac{{6{R_D}}}{{6 + {R_D}}}\\
P' = R{I^2} = \frac{{{U^2}}}{R} = \frac{{{{12}^2}}}{{10 + \frac{{6{R_D}}}{{6 + {R_D}}}}} = 12\\
{R_D} = 3\Omega \\
R = 12\Omega \\
{U_2} = {U_{dm}} = 4,5V\\
{P_{dm}} = \frac{{{U_{dm}}^2}}{{{R_D}}} = \frac{{4,{5^2}}}{3} = 6,75W\\
D(4,5V,6,75W)
\end{array}\)