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Tesseract

Разбалловка

С1  4.00 Find the equivalent resistance $R_{AB}$ between nodes $A$ and $B$.

1
The symmetry is used: nodes are divided in 3 groups based on the distance to node $A$
1.00
2 In blue nodes potential is $(\varphi_A+\varphi_B)/2$ 1.00
3 According to the symmetry $\varphi_A-\varphi_{red} = \varphi_{blue}-\varphi_B$ 1.00
4
Equivalent circuits is drawn or $\varphi_{red}$ is calculated
0.50
5 \[R_{AB}=\frac{2}{3}R\] 0.50