In a center-tapped 240 V single-phase service, the voltage between the two hot legs is

In a center-tapped 240 V single-phase service, the voltage between the two hot legs is

• A. 120
• B. 208
• C. 240
• D. 277

Answer: (C)

In a center-tapped 240 V single-phase service, the two hot legs come from a single transformer with a middle neutral tap. Each leg to neutral is 120 V, and the two legs are 180 degrees out of phase. Because they’re opposite phases, the voltage difference between the two hot legs adds: 120 V + 120 V = 240 V. So the voltage between the hot legs is 240 V. The other numbers come from different systems: 120 V is the leg-to-neutral voltage, 208 V is typical for a 120/208Y three-phase system, and 277 V is the line-to-neutral voltage for a 480V-based system.

In a center-tapped 240 V single-phase service, the two hot legs come from a single transformer with a middle neutral tap. Each leg to neutral is 120 V, and the two legs are 180 degrees out of phase. Because they’re opposite phases, the voltage difference between the two hot legs adds: 120 V + 120 V = 240 V.

So the voltage between the hot legs is 240 V. The other numbers come from different systems: 120 V is the leg-to-neutral voltage, 208 V is typical for a 120/208Y three-phase system, and 277 V is the line-to-neutral voltage for a 480V-based system.