Master Electrician Practice Exam

Which type of electrical system is referenced in the demand load calculation for the building example?

1. 240/480 volt, three-phase system

2. 120/240 volt, single-phase system

3. 120 volt, single-phase system

4. 480 volt, three-phase system

The correct answer is: 120/240 volt, single-phase system

The reference to a 120/240 volt, single-phase system in demand load calculations suggests that this type of electrical system is commonly utilized in residential and light commercial applications. This voltage configuration is practical for supplying standard household voltages, accommodating typical appliances and lighting circuits efficiently. In a residential building example, this system allows for a diverse range of electrical loads, such as lights, outlets, and small appliances, while also providing sufficient power for heavier loads like dryers and electric ranges by utilizing the 240 volt supply. When calculating demand loads, it's essential to account for the maximum expected usage within the system's limitations. A 120/240 volt, single-phase system is often sufficient for most residential structures, ensuring that calculations remain accurate and reflective of actual power requirements. In contrast, the other types of systems presented would be more uncommon for standard residential buildings. A 240/480 volt, three-phase system is generally used in industrial applications, while the 480 volt, three-phase system is harsher and intended for more extensive industrial machinery rather than typical residential needs. Lastly, a 120 volt, single-phase system does not provide the versatility needed for more demanding appliances common in homes.