Đáp án:
Giải thích các bước giải:
a. Mạch $(R_1 // R_2 // R_3) nt (R_4 // R_5)$
Ta có:
$\dfrac{1}{R_{123}} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3}$
$\dfrac{1}{R_{123}} = \dfrac{1}{2,5} +'\dfrac{1}{6} + \dfrac{1}{10} = \dfrac{2}{3}$
Suy ra: $R_{123} = \dfrac{3}{2} = 1,5 (\Omega)$
$\dfrac{1}{R_{45}} = \dfrac{1}{R_4} + \dfrac{1}{R_5} = \dfrac{1}{1,2} + \dfrac{1}{5} = \dfrac{31}{30}$
Suy ra: $R_{45} = \dfrac{30}{31} (\Omega)$
Do đó:
$R_{tđ} = R_{123} + R_{45} = 1,5 + \dfrac{30}{31} = \dfrac{153}{62} (\Omega)$
Khi đó ta có:
$I = I_{123} = I_{45} = \dfrac{U}{R_{tđ}} = \dfrac{6}{\dfrac{153}{62}} = \dfrac{124}{51} (A)$
Suy ra:
$U_{123} = U_1 = U_2 = U_3 = I_{123}.R_{123} = \dfrac{124}{51}.1,5 = \dfrac{62}{17} (V)$
$U_{45} = U_4 = U_5 = I_{45}.R_{45} = \dfrac{124}{51}.\dfrac{30}{31} = \dfrac{40}{17} (V)$
Suy ra:
$I_1 = \dfrac{U_1}{R_1} = \dfrac{\dfrac{62}{17}}{2,5} = \dfrac{124}{85} (A)$
$I_2 = \dfrac{U_2}{R_2} = \dfrac{\dfrac{62}{17}}{6} = \dfrac{31}{51} (A)$
$I_3 = \dfrac{U_3}{R_3} = \dfrac{\dfrac{62}{17}}{10} = \dfrac{31}{85} (A)$
$I_4 = \dfrac{U_4}{R_4} = \dfrac{\dfrac{40}{17}}{1,2} = \dfrac{100}{51} (A)$
$I_5 = \dfrac{U_5}{R_5} = \dfrac{\dfrac{40}{17}}{5} = \dfrac{8}{17} (A)$
