The circuit below shall be given.
1. What is the equivalent resistance $R_{\rm eq}$?
Part of the circuit is shorted. Here the resistors (marked in red) are shorted by the connections marked in blue:
The circuit can then be rearranged for better interpretation:
Therefore, $R_{\rm eq}$ is given as: \begin{align*} R_{\rm eq} &= (2R||2R + R + R)||6R &&+ 6R ||(2R + 2R + 4R||4R) \\ &= (R + R + R)||6R &&+ 6R ||(2R + 2R + 2R) \\ &= 3R||6R &&+ 6R ||6R \\ &= {{3R\cdot 6R}\over{3R+6R}} &&+3R \\ \end{align*}
2. Now the input voltage shall be given as $U_{\rm AB} = 60 ~\rm V$. What is the value for $U$ in the circuit?