Free Construction Electrician Red Seal Examination Practice Questions

Sample Practice Questions

Try these 10 sample questions from the Construction Electrician Red Seal Examination practice bank. Each includes the answer and explanation. Continue with the interactive practice above to review the full question set.

1. 1A construction electrician has isolated a resistor from a de-energized control circuit and needs to measure its electrical resistance. Which single-purpose instrument should be selected?

   1. A.Wattmeter
   2. B.Ammeter
   3. C.OhmmeterCorrect answer: C
   4. D.Voltmeter

   Explanation: The manufacturer states, "To measure the resistance of a circuit, you would use an ohmmeter." With the resistor isolated, an ohmmeter measures its resistance; an ammeter, voltmeter and wattmeter measure current, voltage and power respectively.

   Reference: Electrical Measurements: Units, devices, and formulas — Ohmmeter

2. 2A construction electrician is selecting a stand-alone protective device that will open a receptacle circuit when outgoing and returning currents differ because current is escaping the intended path. Which device has this function?

   1. A.Thermal overload relay
   2. B.Surge protective device
   3. C.Ground-fault circuit interrupterCorrect answer: C
   4. D.Arc-fault circuit interrupter

   Explanation: The Electrical Safety Authority explains, "For ground fault circuit interrupters, essentially it monitors the current going out and coming back." A difference between those currents indicates leakage from the intended circuit. A ground-fault circuit interrupter is designed to respond to that imbalance; the other devices address different protective functions.

   Reference: Arc Fault and Ground Fault Circuit Interrupters — ESA transcript — Differences between AFCIs and GFCIs

3. 3While checking a 36 V DC electric heating circuit, an electrician finds that its two heating resistances of 12 Ω and 6 Ω are connected in series. Assuming ideal components, what current flows through the circuit?

   1. A.3 A
   2. B.9 A
   3. C.2 ACorrect answer: C
   4. D.6 A

   Explanation: OpenStax states, "The equivalent resistance of a set of resistors in a series connection is equal to the algebraic sum of the individual resistances." Fluke states, "current equals voltage divided by resistance." The total is 12 Ω + 6 Ω = 18 Ω, so 36 V ÷ 18 Ω = 2 A. The 3 A and 6 A alternatives omit the 6 Ω and 12 Ω resistance respectively; 9 A comes from treating the resistances as parallel: 36 V ÷ 4 Ω.

   Reference: University Physics Volume 2: Resistors in Series and Parallel — Resistors in Series

4. 4An electrician sets up an AC drive for a motor whose specified constant voltage-to-frequency ratio is based on 230 V at 60 Hz. If the drive is commanded to 30 Hz and must maintain that same ratio, what output voltage should it provide?

   1. A.57.5 V
   2. B.115 VCorrect answer: B
   3. C.230 V
   4. D.460 V

   Explanation: Fluke advises, "Check the voltage/frequency ratio (V/Hz) to ensure it is in specified limits of the motor." Here the specified constant ratio is 230 V / 60 Hz. At 30 Hz the voltage is (230/60) × 30 = 115 V. The 57.5 V choice halves the voltage twice; 230 V leaves voltage unchanged; 460 V reverses the frequency ratio.

   Reference: Five key test points for understanding motor drive efficiency and performance — 3. Drive Output, Tests

5. 5An electrician verifies a newly installed fibre-optic communication link with an optical loss test set, using a correctly established one-jumper reference. Which connection losses at the two ends of the installed link are included in the result?

   1. A.The loss of both end connectionsCorrect answer: A
   2. B.The loss of the source-end connection only
   3. C.The loss of the meter-end connection only
   4. D.The loss of neither end connection

   Explanation: The reference guidance states that the one-jumper method "correctly accounts for the loss of connections at both ends". A one-end result describes the limitation of a two-jumper reference, while excluding both ends is associated with the three-jumper method.

   Reference: Why the 1-Jumper Reference Is Recommended — Selecting the right test reference method, 1-jumper reference

6. 6Before using a hazardous product on a construction site, an electrician checks its WHMIS classification. Which pictogram is assigned to a product's category 1 carcinogenicity hazard?

   1. A.Corrosion
   2. B.Health hazardCorrect answer: B
   3. C.Exclamation mark
   4. D.Skull and crossbones

   Explanation: CCOHS states, "The health hazard pictogram is used for the following classes and categories:" and lists "Carcinogenicity (Category 1, 1A, 1B, and 2)". The pictogram assigned to the specified carcinogenicity classification is therefore health hazard; the other pictograms correspond to other WHMIS hazard classifications.

   Reference: WHMIS - Pictograms — What pictograms are used with WHMIS hazard classes and categories? – Health Hazard

7. 7An electrician checks a single-phase control transformer with 600 primary turns and 60 secondary turns. Assuming ideal operation and 240 V AC on the primary, what secondary voltage should be expected?

   1. A.2.4 V AC
   2. B.24 V ACCorrect answer: B
   3. C.240 V AC
   4. D.2,400 V AC

   Explanation: OpenStax states that "the ratio of the secondary to primary voltages in a transformer equals the ratio of the number of loops in their coils." Thus Vs/Vp = Ns/Np = 60/600 = 0.1, and Vs = 240 V × 0.1 = 24 V AC. The 2.4 V choice uses 0.01 instead of 0.1; 240 V assumes a 1:1 ratio; 2,400 V reverses the turns ratio.

   Reference: College Physics 2e, Transformers — Section 23.7, transformer equation 23.26

8. 8A buried steel tank is protected by an impressed-current system supplied from an AC circuit. Which component converts that supply to the direct current delivered to the protection anodes?

   1. A.Transformer
   2. B.RectifierCorrect answer: B
   3. C.Inverter
   4. D.Autotransformer

   Explanation: The EPA states: "An impressed current system uses a rectifier to convert alternating current to direct current". The rectifier supplies the DC for the anodes; a transformer or autotransformer changes AC voltage, while an inverter converts DC to AC.

   Reference: Release Prevention for Underground Storage Tanks — Cathodic protection

9. 9An electrician checks a six-pole AC induction motor connected to a 60 Hz supply. What is the synchronous speed of the motor's rotating magnetic field?

   1. A.600 rpm
   2. B.900 rpm
   3. C.1,200 rpmCorrect answer: C
   4. D.1,800 rpm

   Explanation: The U.S. Department of Energy says synchronous speed "is always 120 times the line frequency divided by the number of poles." For six poles at 60 Hz, 120 × 60 / 6 = 1,200 rpm. The 600 rpm value uses half the conversion factor; 900 rpm uses eight poles; 1,800 rpm uses four poles. Actual induction-motor rotor speed is lower under load because of slip.

   Reference: Continuous Energy Improvement in Motor Driven Systems — Chapter 4, Synchronous Speed, page 4-5

10. 10A building automation specification requires devices to communicate using the protocol defined by ASHRAE Standard 135. Which protocol should the electrician verify on the controller documentation?

    1. A.Modbus
    2. B.KNX
    3. C.BACnetCorrect answer: C
    4. D.LonWorks

    Explanation: ASHRAE identifies the standard as "ASHRAE 135 A Data Communication Protocol for Building Automation and Control Networks (BACnet)". Modbus, KNX and LonWorks are other real automation networking technologies, but they are not the protocol named by ASHRAE Standard 135.

    Reference: ASHRAE Standard 135 Resource Files — ASHRAE 135, title and purpose