If a _________ is connected between two non-reference nodes, they form a super-node.

The correct answer is option 3):(voltage source)

Concept:

• A supernode is basically a theoretical model in which we consider two non-reference nodes having an ideal voltage source present between them (N1 and N2 in our case), as a single node.
• In simple terms, we combine those two non-reference nodes to make a single node called a “supernode”

• In the above circuit diagram, V1 and V2 forms a supernode
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Additional Information

• A dependent source is a current or voltage source whose value is not fixed (i.e., independent) but rather which depends on some other circuit current or voltage.
• An independent current source is an energy source that pushes a constant flow of electrons through an electrical circuit regardless of the load presented to it
• A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.