In a 120/240 V single-phase service, the voltage between the two hot conductors is

In a 120/240 V single-phase service, the voltage between the two hot conductors is

• A. 240
• B. 120
• C. 277
• D. 208

Answer: (A)

Split-phase service uses two hot conductors that are 180 degrees out of phase, and each hot provides 120 V to neutral. The voltage between the two hot conductors is the sum of those two voltages, so you get 240 V. This is why a standard home panel shows 240 V between the hot legs, with a neutral at the center. The other voltages come from different systems: 277 V line-to-neutral appears in 480Y/277 V systems, and 208 V line-to-line appears in 120/208 V three-phase systems. In a typical 120/240 single-phase setup, you won’t see 277 or 208 between the hot legs—240 V is the correct line-to-line voltage.

Split-phase service uses two hot conductors that are 180 degrees out of phase, and each hot provides 120 V to neutral. The voltage between the two hot conductors is the sum of those two voltages, so you get 240 V. This is why a standard home panel shows 240 V between the hot legs, with a neutral at the center.

The other voltages come from different systems: 277 V line-to-neutral appears in 480Y/277 V systems, and 208 V line-to-line appears in 120/208 V three-phase systems. In a typical 120/240 single-phase setup, you won’t see 277 or 208 between the hot legs—240 V is the correct line-to-line voltage.