\(1\left\{{}\begin{matrix}a,R1ntR2\Rightarrow\left\{{}\begin{matrix}I1=I2=\dfrac{Uab}{R1+R2}=\dfrac{2}{3}A\\U1=I1.R1=\dfrac{2}{3}.20=\dfrac{40}{3}V\Rightarrow U2=I2R2=\dfrac{80}{3}V\end{matrix}\right.\\b,R1nt\left(R2//R3\right)\Rightarrow\left\{{}\begin{matrix}Rtd=R1+\dfrac{R2R3}{R2+R3}=40\Omega\\I1=\dfrac{Uab}{40}=1A\Rightarrow U1=I1R1=20V\\\left(R2=R3\right)\Rightarrow I2=I3=\dfrac{I1}{2}=0,5A\\U2=U3=40-U1=20V\end{matrix}\right.\\c,\Rightarrow d=\sqrt{\dfrac{4S}{\pi}}=\sqrt{\dfrac{4.\dfrac{pL}{R1}}{3,14}}=1,04.10^{-4}m\\\Rightarrow n=\dfrac{L}{C}=\dfrac{10}{2\pi R}=\dfrac{10}{2\pi.0,005}=318\left(vòng\right)\end{matrix}\right.\)
