In Thevenin/Norton circuit equivalence, what does Voc represent?

• A. The voltage across the terminals with the load disconnected.
• B. The short-circuit current at the terminals.
• C. The maximum current through the load.
• D. The supply voltage of a source inside the circuit.

Answer: (A)

The main idea here is the open-circuit voltage across the output terminals. Voc is the voltage you would measure across the external terminals when nothing is connected (the load is disconnected, an open circuit). In a Thevenin/Norton view, this open-circuit voltage sets the Thevenin voltage of the equivalent circuit, because with no load current, there’s no drop across the internal resistance, so the terminal voltage reflects the network’s available voltage.

So why is this the best description? Because Voc captures exactly what the external circuit “sees” with no load: the voltage that would drive any connected load if it were removed. It’s the quantity used to define the Thevenin equivalent voltage source. By contrast, the short-circuit current describes the current when the terminals are directly connected (shorted), not the open-circuit voltage; “maximum current through the load” is not a fixed quantity and depends on the load value, and the “supply voltage of a source inside the circuit” isn’t the terminal voltage measured when the load is removed, since internal drops matter when current flows.