BOC Electrical Systems and Lighting 2

Question 1

A 120-volt circuit feeds a resistive heater with a resistance of 10 ohms. How much current does it draw?

Accepted Answer

12 A

Answer

By Ohm's law, I = V/R = 120 V / 10 Ω = 12 A.

Question 2

Power factor in a building's electrical system is best defined as the ratio of:

Accepted Answer

Real power (kW) to apparent power (kVA)

Answer

Power factor equals kW divided by kVA and shows how effectively current is converted into useful work.

Question 3

Commercial utility demand charges are typically based on which measurement?

Accepted Answer

The highest average kW over a short interval (often 15 minutes) during the billing period

Answer

Demand charges bill the peak average kW recorded over a short demand interval, regardless of total energy use.

Question 4

One footcandle of illuminance is equal to:

Accepted Answer

One lumen per square foot

Answer

A footcandle is the illuminance produced by one lumen evenly spread over one square foot.

Question 5

A Class A GFCI receptacle is designed to trip when it senses a ground-fault current imbalance of about:

Accepted Answer

5 mA

Answer

Class A GFCIs trip at roughly 4–6 mA to protect people from shock.

BOC - Building Operator Certification Practice Test