Đáp án:
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Giải thích các bước giải:
1:
\[\frac{{{U_1}}}{{{U_2}}} = \frac{{{N_1}}}{{{N_2}}} = > {N_2} = {N_1}.\frac{{{U_2}}}{{{U_1}}} = 4400.\frac{{12}}{{220}} = 240vong\]
2:
\[\frac{{{U_1}}}{{{U_2}}} = \frac{{{N_1}}}{{{N_2}}} = > {N_2} = {N_1}.\frac{{{U_2}}}{{{U_1}}} = 240.\frac{{200000}}{{2000}} = 24000vong\]
b> giảm 10000 lần
\[{P_{hp}}' = \frac{{{P_{hp}}}}{{{{100}^2}}} = \frac{{{P_{hp}}}}{{10000}}\]
c>
\[{P_{hp}} = R.\frac{{{P^2}}}{{{U^2}}} = 0,2.\frac{{{{({{5000.10}^3})}^2}}}{{{{200000}^2}}} = 125W\]