Đáp án:
a.$60,5\left( \Omega \right)$
b.$984,375\left( s \right)$
c.$36\left( {kw.h} \right)$
Giải thích các bước giải:
$\begin{array}{l}
a.R = \frac{{U_{dm}^2}}{{{P_{dm}}}} = \frac{{{{220}^2}}}{{800}} = 60,5\left( \Omega \right)\\
b.V = 2,5l \Rightarrow m = 2,5kg\\
{Q_{thu}} = mc\Delta t = 2,5.4200.\left( {100 - 25} \right) = 787500\left( J \right)\\
{Q_{toa}} = {Q_{thu}}\\
\Rightarrow Pt = {Q_{thu}}\\
\Rightarrow 800.t = 787500\\
\Rightarrow t = 984,375\left( s \right)\\
c.P = 800w = 0,8kw\\
A = Pt = 0,8.1,5,30 = 36\left( {kw.h} \right)
\end{array}$