Câu hỏi 25

Theo bài ra ta có: 

\(\left\{ \matrix{
{{{P^2}R} \over {U_1^2c{\rm{o}}{{\rm{s}}^2}\varphi }} = 1 - {H_1} \hfill \cr
{{{P^2}R} \over {U_2^2c{\rm{o}}{{\rm{s}}^2}\varphi }} = 1 - {H_2} \hfill \cr} \right. \Rightarrow {{{U_2}} \over {{U_1}}} = \sqrt {{{1 - {H_1}} \over {1 - {H_2}}}} = \sqrt {{{1 - 0,8} \over {1 - 0,95}}} \Leftrightarrow {{{U_2}} \over 2} = 2 \Rightarrow {U_2} = 4kV\)