If a 120 V source is shorted through a 0.2 Ω resistance, what is the short-circuit current?

If a 120 V source is shorted through a 0.2 Ω resistance, what is the short-circuit current?

• A. 600 A
• B. 12 A
• C. 6000 A
• D. 120 A

Answer: (A)

Short-circuit current follows Ohm’s law: I = V / R. With a 120 V source and a short through 0.2 Ω, the current is 120 / 0.2 = 600 A. A very small path resistance lets a large current flow, which is why protection devices matter. If the current were 12 A, the total resistance would be about 10 Ω; 6000 A would require only 0.02 Ω; 120 A would need about 1 Ω. The given 0.2 Ω path yields the 600 A result.

Short-circuit current follows Ohm’s law: I = V / R. With a 120 V source and a short through 0.2 Ω, the current is 120 / 0.2 = 600 A. A very small path resistance lets a large current flow, which is why protection devices matter. If the current were 12 A, the total resistance would be about 10 Ω; 6000 A would require only 0.02 Ω; 120 A would need about 1 Ω. The given 0.2 Ω path yields the 600 A result.