PC Study Guide 2026
Everything you need to pass the PC exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 PC Exam Format at a Glance
📚 PC Topics to Study (21)
✍️ Sample PC Questions & Answers
1. What is a circuit breaker used for in electrical systems?
A circuit breaker is a crucial safety device in electrical systems, designed to automatically interrupt the electrical flow in case of overloads or short circuits. When an excessive current is detected, the breaker 'trips,' cutting power to prevent damage to wiring and appliances. This protects against overheating and potential electrical fires, enhancing overall system safety.
2. When installing conductors in parallel, which of the following is a requirement according to NEC 310.10(G)?
NEC 310.10(G) requires that when conductors are run in parallel, they must be the same length, made of the same conductor material, have the same circular mil area (size), have the same insulation type, and be terminated in the same manner. This ensures that the current divides evenly between the conductors.
3. What is the apparent power (in kVA) of a three-phase motor with a line voltage of 480V, drawing a line current of 60A?
The formula for apparent power (S) in a three-phase system is S = V_line * I_line * √3. Plugging in the given values: S = 480V * 60A * 1.732 = 49,881.6 VA. To convert from VA to kVA, divide by 1,000. S = 49,881.6 / 1000 ≈ 50.0 kVA.
4. What is the difference between alternating current (AC) and direct current (DC)?
Alternating Current (AC) is characterized by its periodic reversal of direction, meaning the current flow changes back and forth. In contrast, Direct Current (DC) flows consistently in a single direction. This fundamental difference in current behavior dictates how electricity is generated, transmitted, and used in various applications, from household outlets (AC) to batteries (DC).
5. A dry-type transformer with an 80°C rise rating is installed in a room with a 40°C ambient temperature. What is the maximum operating winding temperature?
Maximum winding temperature equals ambient temperature plus temperature rise: 40°C + 80°C = 120°C, which must remain within the insulation class rating.
6. A 75 kVA single-phase transformer supplies a 60 kW resistive load at unity power factor. What is the approximate load percentage?
At unity power factor, kVA equals kW, so the load percentage is 60 kW ÷ 75 kVA = 80%.