2020 Edition

# Electrician Math Practice Test

Take a free Electrician Math Practice Test to see what kind of math questions are on actual electrician license exams.  Most states require an electrician to pass an exam to receive a journeyman or master electrician license.  State exams cover such areas as power and current formulas, branch circuit load calculations, voltage drop, raceway fill and sizing and more.

For help with math calculations on electrician license exams, the following two books written by Ray Holder (Master Electrician and Certified Electrical Trade Instructor) focus on math and show you, in a step-by-step way, how to solve electrician math problems:

 1. A single-phase, 240-volt, 15 kVA standby generator may be loaded to a MAXIMUM of _____ per line. a. 62.50 amperes b. 31.25 amperes c. 41.66 amperes d. 52.50 amperes
 2. When installing NM type cable in a residential construction project, you find that you are compelled to use a shallow square metal box, 4" x 1.5" deep. If you are to use this box as a junction box for wiring in a finished area wall, how many cubic inches will the plaster ring have to be, minimum, if you have five (5) number twelve two conductor cables with ground wires (#12/2 +gnd) coming into this box? a. 12.75 cu. in. b. 3.75 cu. in. c. 1 cu. in. d. 1.5 cu. in.
 3. Based on the circumstances described in the previous question, what is the minimum cubic inch size of the plaster ring required if you were to install a standard duplex outlet at this location? a. 12.75 cu. in. b. 3.75 cu. in. c. 8.25 cu. in. d. 6 cu. in.
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 4. Where an 80-ampere, 240-volt, single-phase load is located 200 feet from a panelboard and is supplied with size 3 AWG copper conductors with THWN insulation, what is the approximate voltage-drop on the circuit?(K = 12.9) A. 6.0 volts B. 4.0 volts C. 9.2 volts D. 7.84 volts
 5. You are installing a conduit on a rooftop to supply power to an air conditioning unit. The unit requires a 60 ampere 240 volt supply, with a nameplate load amperage of 45.5A. The rooftop will regularly reach 145°F in the summer, as you are installing above dark rooftop material, though your conduit will be 40" above the rooftop. What is the minimum size THWN-2 copper conductor that you can use? a. #8 b. #6 c. #4 d. #3
 6. You are installing 1.5" metal conduit on the ceiling of an unfinished basement to connect a sub-panel to the service equipment. In the conduit you will install 4- #1 THWN copper conductors plus an uninsulated #6 equipment grounding conductor. For ease of installation, you will add a junction box in a straight section of the raceway, where you will also splice the wires. This is the only raceway in this box. What is the minimum required length of the box? a. 9" b. 12" c. 14" d. 6"
 7. When a retail furniture store has 80 continuous linear feet of display show window, the NEC mandates at LEAST _____ receptacle outlets be provided within 18 inches of the top of the show window for the show window lighting. A. six B. seven C. eight D. nine
 8. You are preparing to pull in the wires from service equipment to a sub-panel through parallel conduits that you have already installed. It is a 400 ampere three phase four wire feeder, plus the equipment grounding conductor. Due to the distance, to accommodate voltage drop you have to increase your ungrounded conductors from 3/0 cu to #250 kcmil. What minimum size will your copper (cu) equipment grounding conductor need to be? a. #1 al b. #3 cu c. #2/0 cu d. #1 cu
 9. Determine the MAXIMUM number of 125-volt, general-purpose receptacles the NEC permits to be protected by a 20-ampere, 120-volt, single-pole inverse time circuit breaker in a commercial occupancy. A. 18 B. 15 C. 13 D. 10
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 10. Where a rooftop mounted air-conditioning unit is supplied with three (3) size 8 AWG THWN copper conductors, enclosed in an electrical metallic tubing (EMT) within three (3) inches of the rooftop, and exposed to direct sunlight and an ambient temperature of 100 degrees F, the allowable ampacity of the conductors is _____ . A. 50 amperes B. 44 amperes C. 29 amperes D. 25 amperes
 11. You need to install Sch. 80 PVC conduit on an exposed exterior wall in straight runs with a junction box at each end. This area is subject to a daily temperature fluctuation that is most extreme in the winter, when it can drop to -30° F overnight, and then rise to 45° F in the early afternoon. How long can the conduit runs be, individually, before you need an expansion coupling? (Give answer in whole feet) a. 8' b. 26' c. 64' d. None needed
 12. You need to install a feeder to a subpanel in a newly constructed remote workshop at a single family dwelling. The source power is 120/240V single phase. The load in the workshop is engineered to be 85 amperes continuous at 240V, and a non-continuous 240V load of 35 amperes. The wire length will be 245' from the main service termination point to the workshop termination point. Using the Informational notes in Article 215 and the following formula, size the THWN copper feeder wires to provide reasonable efficiency of operation by preventing excessive voltage drop (keeping the wires as small as possible). The formula is: VD = 2 x L x R x I ÷ 1000. VD = voltage drop, L = length, R = resistance in /1000'. a. #1/0 THWN copper b. #4/0 THWN copper c. #350 kcmil copper d. #500 kcmil copper
 13. In the circumstances described in the previous question, the breaker feeding the workshop is a 150A 240V 2 pole device. What is the minimum required size for the copper Equipment Grounding Conductor in THWN insulation? a. #8 THWN b. #6 THWN c. #3 THWN d. #1/0 THWN
 14. A local appliance store, as part of a publicity campaign, has donated 12 electric cooktop stoves to your local school's Home Economics classroom. That's great, but the school's current cooktops are all gas appliances. The school would therefore like to know if their existing electrical system has the capacity to add these cooktops. Given the following details, what load will be added to the school's electrical system? Each unit is 8,600 watts @ 240V, which fortunately matches the school's single phase system. a. 116 amperes b. 138 amperes c. 280 amperes d. 430 amperes
 15. For each individual cooktop from the previous question, there will be a dedicated branch circuit. What is each circuit's individual ampacity? a. 72 amperes b. 36 amperes c. 40 amperes d. 11.5 amperes
 16. You have 132 #14 THWN copper wires used for signaling in a Class 1 system, and 5 #12 THWN spare copper conductors. To get the wiring from the PLC to the machinery, you will use EMT conduit. What is the minimum size that the EMT will be required to be? a. 2.5" b. 2" c. 4" d. 3"
 17. At the job from the previous question, the site engineer informs you that 4 of the spare #12 wires need to be used as power supply conductors for components on the same machinery. The maximum current carried by any of the signaling conductors is 0.5 amperes. What is the maximum ampacity of the power supply conductors, assuming no temperature or voltage drop limitations apply? a. 10 amperes b. 16 amperes c. 20 amperes d. 25 amperes
 18. In the interior of a finished commercial facility, you are asked to add a new 100 ampere subpanel, fed with a 100A 3 phase 4 wires plus ground feeder from the main service equipment, which is sitting 50' away. Both the new subpanel and the existing main are surface mount units, and you can install surface mounted EMT conduit. You are given no details of what the load will be. Without applying any exceptions or special conditions requirements, what is the minimum THWN copper wire size that you can use for the current carrying conductors? a. #4 THWN b. #2 THWN c. #3 THWN d. #1 THWN
 19. You need to install some EMT conduit for feeder conductors. The conductors are all copper with THWN insulation. There are 3 #500 kcmil wires and 1 #3 wire. What is the smallest size of EMT that the NEC will allow? a. 2.5" b. 3" c. 3.5" d. 4"
 20. From the previous question, you find that you have to change the conduit routing, and now a portion will have to use PVC conduit, which has to be 3" to have sufficient size. To transition between the two conduits, you will use a pull box, entering from opposite sides. What minimum size will it have to be - without splicing the wires or applying any exceptions? a. 18" between conduits b. 20" between conduits c. 24" between conduits d. 30" between conduits

Quality starts with...
...who wrote the material.
Our practice exam writers:
Ray Holder