Question

Cho R1=R2=R3=5Ω; R5=6Ω; U=24V

P3=7,2W. Tinh P4.

Answer 1

\(R_5nt\left[\left(R_1ntR_3\right)//\left(R_2ntR_4\right)\right]\)

\(\Rightarrow P_3=7,2\left(W\right)\Rightarrow I_3^2R_3=7,2\Rightarrow I_3=1,2\left(A\right)\)

\(I_3=I_1=1,2\left(A\right)\Rightarrow U_{13}=I_{13}.R_{13}=I_3.\left(R_1+R_3\right)=1,2.5.2=12\left(V\right)\)

\(\Rightarrow U_{13}=U_{24}=12\left(V\right)\)

\(\Rightarrow U_5=U-U_{13}=24-12=12\left(V\right)\)

\(\Rightarrow I_5=\frac{U_5}{R_5}=\frac{12}{6}=2\left(A\right)\)

\(\Rightarrow I_2=I_4=I_5-I_3=2-1,2=0,8\left(A\right)\)

\(\Rightarrow R_{24}=\frac{U_{24}}{I_{24}}=\frac{12}{0,8}=15\left(\Omega\right)\)

\(\Rightarrow R_4=15-5=10\left(\Omega\right)\Rightarrow P_4=I^2_4.R_4=0,8^2.10=6,4\left(W\right)\)