Find the voltage at node 'b' in the given circuit.

The correct answer is option 3) -12 V

Concept:

The nodal analysis:

• Nodal Voltage Analysis uses the “Nodal” equations of Kirchhoff’s first law to find the voltage potentials around the circuit.
• So by adding together all these nodal voltages the net result will be equal to zero.
• If there are “n” nodes in the circuit there will be “n-1” independent nodal equations and these alone are sufficient to describe and hence solve the circuit.
• At each node point write down Kirchhoff’s first law equation(KCL), that is: “the currents entering a node are exactly equal in value to the currents leaving the node” then express each current in terms of the voltage across the branch using Ohm's law.
• So the nodal analysis is primarily based on the application of KCL and Ohm's law.
• For “n” nodes, one node will be used as the reference node and all the other voltages will be referenced or measured with respect to this common node

Calculation:

The given circuit is 

The node voltage at b 12-V voltage source. 

v_{b ​} =−12 V