350 QUESTIONS AND ANSWERS
1. Q: What is Ohm's Law? ANSWER Ohm's Law states that voltage (V)
equals current (I) multiplied by resistance (R): V = I × R
2. Q: What is the standard voltage for most commercial lighting circuits in
California? ANSWER 120V, 208V, 240V, 277V, and 480V are common
commercial voltages
3. Q: What does AC stand for in electrical terms? ANSWER Alternating
Current - current that changes direction periodically
4. Q: What is the frequency of AC power in the United States? ANSWER
60 Hz (60 cycles per second)
5. Q: What is the difference between voltage and current? ANSWER
Voltage is electrical pressure (measured in volts), current is the flow of
electrons (measured in amperes)
6. Q: What is electrical power measured in? ANSWER Watts (W) or
kilowatts (kW)
7. Q: How do you calculate electrical power? ANSWER Power = Voltage ×
Current (P = V × I) or Power = Voltage² ÷ Resistance (P = V²/R)
8. Q: What is a conductor? ANSWER A material that allows electrical
current to flow easily, such as copper or aluminum wire
9. Q: What is an insulator? ANSWER A material that resists the flow of
electrical current, used to prevent unwanted current flow
10. Q: What is electrical resistance measured in? ANSWER Ohms (Ω)
11. Q: What happens to current when voltage increases and resistance
stays constant? ANSWER Current increases proportionally (I = V/R)
12. Q: What is a short circuit? ANSWER An unintended path of low
resistance that allows excessive current flow
,13. Q: What is an open circuit? ANSWER A break in the electrical path that
prevents current flow
14. Q: What is electrical inductance? ANSWER The property of a circuit that
opposes changes in current flow
15. Q: What is capacitance? ANSWER The ability to store electrical energy
in an electric field
16. Q: What is impedance? ANSWER The total opposition to AC current
flow, combining resistance, inductance, and capacitance
17. Q: What is the difference between single-phase and three-phase power?
ANSWER Single-phase has one alternating voltage, three-phase has three
alternating voltages 120° apart
18. Q: What is a neutral conductor? ANSWER The conductor that carries
return current in AC circuits, typically connected to ground
19. Q: What is a ground conductor? ANSWER A conductor that provides a
safe path to earth for fault currents
20. Q: What is voltage drop? ANSWER The reduction in voltage along a
conductor due to its resistance
21. Q: Why is voltage drop important in lighting circuits? ANSWER
Excessive voltage drop reduces light output and can cause equipment
malfunction
22. Q: What is the maximum allowable voltage drop for branch circuits per
NEC? ANSWER 5% for branch circuits (3% for feeders, 2% for branch
circuits is recommended)
23. Q: What causes power factor in AC circuits? ANSWER The phase
difference between voltage and current due to reactive components
24. Q: What is a good power factor value? ANSWER As close to 1.0 (unity)
as possible; 0.85 or higher is typically acceptable
25. Q: What is reactive power? ANSWER Power that oscillates between
source and load, measured in VARs (Volt-Amperes Reactive)
26. Q: What is apparent power? ANSWER The total power in an AC circuit,
measured in VA (Volt-Amperes)
27. Q: How do you calculate true power from apparent power? ANSWER
True Power = Apparent Power × Power Factor
, 28. Q: What is harmonics in electrical systems? ANSWER Frequencies that
are multiples of the fundamental 60 Hz frequency
29. Q: What can cause harmonics in lighting systems? ANSWER Electronic
ballasts, LED drivers, and other electronic devices
30. Q: What is Total Harmonic Distortion (THD)? ANSWER A measure of
how much harmonic content is present in a waveform
31. Q: What is electrical load? ANSWER Any device or equipment that
consumes electrical power
32. Q: What is demand load? ANSWER The maximum load expected to be
operating at any given time
33. Q: What is connected load? ANSWER The total load of all devices
connected to a circuit or system
34. Q: What is load diversity? ANSWER The concept that not all loads
operate simultaneously
35. Q: What is a load calculation? ANSWER The process of determining the
electrical demand for a system or circuit
36. Q: What is conductor ampacity? ANSWER The maximum current a
conductor can carry continuously under specific conditions
37. Q: What factors affect conductor ampacity? ANSWER Temperature,
insulation type, number of conductors, and installation method
38. Q: What is derating? ANSWER Reducing conductor ampacity due to
adverse conditions
39. Q: When must conductors be derated? ANSWER When ambient
temperature exceeds 86°F or when more than 3 current-carrying conductors are
bundled
40. Q: What is the ampacity of 12 AWG THWN copper wire at 75°C?
ANSWER 25 amperes
41. Q: What is the ampacity of 10 AWG THWN copper wire at 75°C?
ANSWER 35 amperes
42. Q: What is wire gauge measured by? ANSWER AWG (American Wire
Gauge) - smaller numbers indicate larger wire
43. Q: What is the relationship between wire gauge and current capacity?
ANSWER Larger wire (smaller AWG number) can carry more current
1. Q: What is Ohm's Law? ANSWER Ohm's Law states that voltage (V)
equals current (I) multiplied by resistance (R): V = I × R
2. Q: What is the standard voltage for most commercial lighting circuits in
California? ANSWER 120V, 208V, 240V, 277V, and 480V are common
commercial voltages
3. Q: What does AC stand for in electrical terms? ANSWER Alternating
Current - current that changes direction periodically
4. Q: What is the frequency of AC power in the United States? ANSWER
60 Hz (60 cycles per second)
5. Q: What is the difference between voltage and current? ANSWER
Voltage is electrical pressure (measured in volts), current is the flow of
electrons (measured in amperes)
6. Q: What is electrical power measured in? ANSWER Watts (W) or
kilowatts (kW)
7. Q: How do you calculate electrical power? ANSWER Power = Voltage ×
Current (P = V × I) or Power = Voltage² ÷ Resistance (P = V²/R)
8. Q: What is a conductor? ANSWER A material that allows electrical
current to flow easily, such as copper or aluminum wire
9. Q: What is an insulator? ANSWER A material that resists the flow of
electrical current, used to prevent unwanted current flow
10. Q: What is electrical resistance measured in? ANSWER Ohms (Ω)
11. Q: What happens to current when voltage increases and resistance
stays constant? ANSWER Current increases proportionally (I = V/R)
12. Q: What is a short circuit? ANSWER An unintended path of low
resistance that allows excessive current flow
,13. Q: What is an open circuit? ANSWER A break in the electrical path that
prevents current flow
14. Q: What is electrical inductance? ANSWER The property of a circuit that
opposes changes in current flow
15. Q: What is capacitance? ANSWER The ability to store electrical energy
in an electric field
16. Q: What is impedance? ANSWER The total opposition to AC current
flow, combining resistance, inductance, and capacitance
17. Q: What is the difference between single-phase and three-phase power?
ANSWER Single-phase has one alternating voltage, three-phase has three
alternating voltages 120° apart
18. Q: What is a neutral conductor? ANSWER The conductor that carries
return current in AC circuits, typically connected to ground
19. Q: What is a ground conductor? ANSWER A conductor that provides a
safe path to earth for fault currents
20. Q: What is voltage drop? ANSWER The reduction in voltage along a
conductor due to its resistance
21. Q: Why is voltage drop important in lighting circuits? ANSWER
Excessive voltage drop reduces light output and can cause equipment
malfunction
22. Q: What is the maximum allowable voltage drop for branch circuits per
NEC? ANSWER 5% for branch circuits (3% for feeders, 2% for branch
circuits is recommended)
23. Q: What causes power factor in AC circuits? ANSWER The phase
difference between voltage and current due to reactive components
24. Q: What is a good power factor value? ANSWER As close to 1.0 (unity)
as possible; 0.85 or higher is typically acceptable
25. Q: What is reactive power? ANSWER Power that oscillates between
source and load, measured in VARs (Volt-Amperes Reactive)
26. Q: What is apparent power? ANSWER The total power in an AC circuit,
measured in VA (Volt-Amperes)
27. Q: How do you calculate true power from apparent power? ANSWER
True Power = Apparent Power × Power Factor
, 28. Q: What is harmonics in electrical systems? ANSWER Frequencies that
are multiples of the fundamental 60 Hz frequency
29. Q: What can cause harmonics in lighting systems? ANSWER Electronic
ballasts, LED drivers, and other electronic devices
30. Q: What is Total Harmonic Distortion (THD)? ANSWER A measure of
how much harmonic content is present in a waveform
31. Q: What is electrical load? ANSWER Any device or equipment that
consumes electrical power
32. Q: What is demand load? ANSWER The maximum load expected to be
operating at any given time
33. Q: What is connected load? ANSWER The total load of all devices
connected to a circuit or system
34. Q: What is load diversity? ANSWER The concept that not all loads
operate simultaneously
35. Q: What is a load calculation? ANSWER The process of determining the
electrical demand for a system or circuit
36. Q: What is conductor ampacity? ANSWER The maximum current a
conductor can carry continuously under specific conditions
37. Q: What factors affect conductor ampacity? ANSWER Temperature,
insulation type, number of conductors, and installation method
38. Q: What is derating? ANSWER Reducing conductor ampacity due to
adverse conditions
39. Q: When must conductors be derated? ANSWER When ambient
temperature exceeds 86°F or when more than 3 current-carrying conductors are
bundled
40. Q: What is the ampacity of 12 AWG THWN copper wire at 75°C?
ANSWER 25 amperes
41. Q: What is the ampacity of 10 AWG THWN copper wire at 75°C?
ANSWER 35 amperes
42. Q: What is wire gauge measured by? ANSWER AWG (American Wire
Gauge) - smaller numbers indicate larger wire
43. Q: What is the relationship between wire gauge and current capacity?
ANSWER Larger wire (smaller AWG number) can carry more current
