Question

Đèn : 140V - 490W

R1 = 30 ôm

Rb = 20 ôm

U = 250 không đổi

LÀM GẤP GIÚP MÌNH VỚI Ạ MÌNH CẦN GẤP LẮM

Answer 1

MCD: \(R1//\left(R2ntR3\right)\)

\(\Rightarrow U=U1=U23=250V\)

\(\Rightarrow\left\{{}\begin{matrix}U3=140V\\U2=U23-U3=250-140=110V\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}I1=U1:R1=250:30=\dfrac{25}{3}A\\I2=U2:R2=110:20=\dfrac{11}{2}A\\I3=I2=\dfrac{11}{2}A\left(R1ntR3\right)\end{matrix}\right.\)

Answer 2

   \(U_Đ=140V;I_Đ=\dfrac{P_Đ}{U_Đ}=\dfrac{490}{140}=3,5A\)

   \(R_Đ=\dfrac{U^2_Đ}{P_Đ}=\dfrac{140^2}{490}=40\Omega\)

   \(R_2=R_{Đ+b}=R_Đ+R_b=40+20=60\Omega\)

   \(R_{tđ}=\dfrac{R_1\cdot R_2}{R_1+R_2}=\dfrac{30\cdot60}{30+60}=20\Omega\)

   \(U_1=U_m=250V\)

   \(I_1=\dfrac{U_1}{R_1}=\dfrac{250}{30}=\dfrac{25}{3}A\)

   \(I_2=\dfrac{U}{R_2}=\dfrac{250}{60}=\dfrac{25}{6}A\)\(\Rightarrow I_Đ=I_b=\dfrac{25}{6}A\)