In a Thevenin circuit with V_th = 12 V and R_th = 2 Ω feeding a short-circuited load (0 Ω), what is the current through the source immediately after connection?

• A. 0 A
• B. 6 A
• C. 12 A
• D. 3 A

Answer: (B)

When the load is shorted, the current is the short-circuit current, set by the Thevenin resistance only. You have a 12 V source in series with 2 Ω, so the current is I = V_th / R_th = 12 V / 2 Ω = 6 A. The current travels from the positive terminal, through the short, back to the source. This is the maximum current the Thevenin circuit can deliver with that internal resistance.