List of top Network Theory Questions on Nodal Analysis

In the given circuit, all resistors are 1 k$\Omega$. A 1 mA current source is connected between the top and bottom nodes. A 6 V source connects the midpoints of the two vertical branches as shown. Find the output voltage $V_0$. 
 

For the circuit shown in the figure, $V_{1 = 8$ V, DC and $I_{1} = 8$ A, DC. The voltage $V_{ab}$ in Volts is \underline{\hspace{1cm}} (Round off to 1 decimal place).} \begin{center} \includegraphics[width=0.5\textwidth]{14.jpeg} \end{center}