Question

Am si eu nevoie de ajutor va rog, 1 SI 2!!

Answer 1

[tex]1)Se~da:\\ \\ R_{1}=R_{2}=R_{4}=10\Omega\\ \\ R_{3}=40\Omega\\ \\ R=?\Omega\\ \\ \\ Formule:\\ \\ R=R_{1}+R_{23}+R_{4}\\ \\ \\ \frac 1{R_{23}}=\frac 1{R_{2}}+\frac 1{R_{3}}\\ \\ \frac 1{R_{23}}=\frac{R_{2}+R_{3}}{R_{2}\times R_{3}}\\ \\ R_{23}=\frac {R_{2}\times R_{3}}{R_{2}+R_{3}}\\ \\ \\ R=R_{1}+\frac {R_{2}\times R_{3}}{R_{2}+R_{3}}+R_{4}\\ \\ \\ Calcule:\\ \\ R=10+\frac {10\times 40}{10+40}+10=28\Omega\\ \\ \\[/tex]



[tex]2)Se~da:\\ \\ R_{1}=15\Omega\\ \\ R_{2}=20\Omega\\ \\ R_{3}=50\Omega\\ \\ a)R=?\Omega\\ \\ b)U=6V\\ \\ I_{1};I_{2};I_{3};I_{4}=?A\\ \\ \\ Formule:\\ \\ a)R=R_{1}+R_{234}\\ \\ \\ \frac 1{R_{234}}=\frac 1{R_{23}}+\frac 1{R_{4}}\\ \\ R_{23}=R_{2}+R_{3}\Rightarrow \frac 1{R_{234}}=\frac 1{R_{2}+R_{3}}+\frac 1{R_{4}}\\ \\ \frac 1{R_{234}}=\frac{R_{2}+R_{3}+R_{4}}{R_{4}\times (R_{2}+R_{3})}\\ \\ R_{234}=\frac{R_{4}\times (R_{2}+R_{3})}{R_{2}+R_{3}+R_{4}}\\ \\ \\[/tex]



[tex]b)I_{1}=I_{234}=I\\ \\ I=\frac UR\Rightarrow I_{1}=\frac UR\\ \\ \\ U_{234}=U_{23}=U_{4}\\ \\ U_{234}=R_{234}\times I_{234}\\ \\ U_{234}=R_{234}\times \frac UR\\ \\ \\ I_{23}=I_{2}=I_{3}\\ \\ I_{23}=\frac {U_{23}}{R_{23}}\Leftrightarrow I_{23}=\frac {U_{23}}{R_{2}+R_{3}}\\ \\ \\ I_{2}=I_{3}=\frac{R_{234} \times U}{R \times (R_{2}+R_{3})}\\ \\ \\ I_{4}=\frac {U_{4}}{R_{4}}\\ \\ I_{4}=\frac{R_{234} \times U}{R \times R_{4}}\\ \\ \\ [/tex]


[tex]Sint~sigur~ca~autorii~au~uitat~sa~scrie~valoarea~R_{4}!\\ \\ Formulele~sint~bune~de~ceva~inlocuiesti~si~aflii![/tex]