Câu 3: 

Công suất hao phí là:

\({P_{hp}} = {\left( {\dfrac{P}{U}} \right)^2}R = {\left( {\dfrac{{{{10000.10}^3}}}{{{{100.10}^3}}}} \right)^2}.0,{1.10^3} = {10^6}W\)

Câu 4: 

a) Hình vẽ

b) Ta có: 

\(\begin{array}{l}
\dfrac{{AB}}{{A'B'}} = \dfrac{{OA}}{{OA'}} = \dfrac{6}{{OA'}}\\
\dfrac{{AB}}{{A'B'}} = \dfrac{{OI}}{{A'B'}} = \dfrac{{OF'}}{{OA' - OF'}} = \dfrac{4}{{OA' - 4}}\\
 \Rightarrow \dfrac{6}{{OA'}} = \dfrac{4}{{OA' - 4}} \Rightarrow OA' = 12cm\\
 \Rightarrow \dfrac{{AB}}{{A'B'}} = \dfrac{6}{{12}} = \dfrac{1}{2} \Rightarrow A'B' = 1cm
\end{array}\)

Câu 5: 

a) Ta có: 

\(\dfrac{{{U_1}}}{{{U_2}}} = \dfrac{{{N_1}}}{{{N_2}}} \Rightarrow \dfrac{{{U_1}}}{{100}} = \dfrac{{1000}}{{5000}} \Rightarrow {U_1} = 20kV\)

b) Công suất hao phí là:

\({P_{hp}} = {\left( {\dfrac{P}{{{U_2}}}} \right)^2}R = {\left( {\dfrac{{{{10000.10}^3}}}{{{{100.10}^3}}}} \right)^2}.0,{1.10^3} = {10^6}W\)

Câu 6:

a) Ảnh ảo, cùng chiều, lớn hơn vật

b) Ta có: 

\(\begin{array}{l}
\dfrac{{AB}}{{A'B'}} = \dfrac{{OA}}{{OA'}} = \dfrac{5}{{OA'}}\\
\dfrac{{AB}}{{A'B'}} = \dfrac{{OI}}{{A'B'}} = \dfrac{{OF'}}{{OA' + OF'}} = \dfrac{{10}}{{OA' + 10}}\\
 \Rightarrow \dfrac{5}{{OA'}} = \dfrac{{10}}{{OA' + 10}} \Rightarrow OA' = 10cm\\
 \Rightarrow \dfrac{{AB}}{{A'B'}} = \dfrac{5}{{10}} = \dfrac{1}{2} \Rightarrow A'B' = 6cm
\end{array}\)