Đáp án:
\(\begin{array}{l}
41.D.100\Omega \\
{R_1} = 10R = 10.10 = 100\Omega \\
42.B\\
43.A.{R_1} = 2{R_2}\\
{m_1} = {m_2} \Rightarrow {V_1} = {V_2}\\
\Rightarrow {S_1}{l_1} = {S_2}{l_2}\\
\Rightarrow {S_1} = \dfrac{{{S_2}{l_2}}}{{{l_1}}} = \dfrac{{{S_2}{l_2}}}{{2{l_2}}} = 0,5{S_2}\\
{R_1} = \rho \dfrac{{{l_1}}}{{{S_1}}} = \rho \dfrac{{2{l_2}}}{{0,5{S_2}}} = 4.\rho \dfrac{{{l_2}}}{{{S_2}}} = 4{R_2}\\
44.C.{R_1} = 4{R_2}\\
{r_2} = 2{r_1} \Rightarrow {S_2} = 4{S_1}\\
{R_2} = \rho \dfrac{l}{{{S_2}}} = \rho \dfrac{l}{{4{S_1}}} = \dfrac{1}{4}.\rho \dfrac{l}{{{S_1}}} = \dfrac{1}{4}{R_1}\\
\Rightarrow {R_1} = 4{R_2}\\
45.C.{R_1} = \dfrac{1}{2}{R_2}\\
{d_1} = 2{d_2} \Rightarrow {S_1} = 4{S_2}\\
{R_1} = \rho \dfrac{{{l_1}}}{{{S_1}}} = \rho \dfrac{{2{l_2}}}{{4{S_2}}} = \dfrac{1}{2}.\rho \dfrac{l}{{{S_2}}} = \frac{1}{2}{R_2}
\end{array}\)
