Red Seal Construction Electrician Practice Exam

What is the standard voltage supply in residential wiring?

1. 100/200 volts AC

2. 120/240 volts AC

3. 240/480 volts AC

4. 120/120 volts AC

The correct answer is: 120/240 volts AC

The typical standard voltage supply in residential wiring, which is 120/240 volts AC, is designed to accommodate a variety of household appliances and lighting systems. The 120 volts is primarily used for standard outlets and smaller, less power-intensive devices, while the 240 volts is utilized for larger appliances that require more power, such as dryers and ovens. This configuration allows for flexibility and efficiency in the electrical system, as ordinary devices can run on 120 volts, while demanding appliances have access to the higher voltage. The split-phase system in residential wiring not only enables this dual voltage supply but also helps balance the electrical load across the two phases, improving safety and performance. The other options depict voltages not typically used in standard residential settings. For example, 100/200 volts AC is not standard in North American homes, while 240/480 volts AC is more common in industrial settings for larger machinery. Lastly, 120/120 volts AC does not reflect the dual-phase distribution typical in residential wiring, as it lacks the higher voltage needed for larger appliances.