Question

Trong hình bên C1 = 30μF, C2 = 6μF, C3 = C4 = 4μF, C5 = 8μF. U = 900V.
Tính hiệu điện thế giữa A và B?

Answer 1

\(C_1ntC_2\Rightarrow C_{12}=\dfrac{C_1\cdot C_2}{C_1+C_2}=\dfrac{3\cdot6}{3+6}=2\mu F\)

\(C_3ntC_4\Rightarrow C_{34}=\dfrac{C_3\cdot C_4}{C_3+C_4}=\dfrac{4\cdot4}{4+4}=2\mu F\)

\(C_{1234}=C_{12}+C_{34}=2+2=4\mu F\)

\(C_{mạch}=C_5+C_{1234}=4+8=12\mu F\)

\(\dfrac{U_{12}}{U_{mạch}}=\dfrac{U_{34}}{U_{mạch}}=\dfrac{C_5}{C_{mạch}}\Rightarrow U_{12}=U_{34}=\dfrac{4}{12}\cdot900=300V\)

\(\Rightarrow U_2=\dfrac{C_2}{C_1+C_2}\cdot U_{12}=\dfrac{6}{3+6}\cdot300=200V\)

\(U_4=\dfrac{C_4}{C_3+C_4}\cdot U_{34}=\dfrac{4}{4+4}\cdot300=150V\)

\(U_{AB}=U_2-U_4=200-150=50V\)