Journeyman Electrician Practice Test 18

Question 1: A good grounding system can also protect the electrical system from lightning effects.

• True
• False

Question 2: The resistance between a driven pipe or ground rod, and the earth should not exceed ............... ohms.

• 25
• 30
• 20

NEC Reference: NEC 250.84

Question 3: If a house having less than two branch circuits with an ampere rating of 25 ampere. what is the minimum wire size that can be used?

• No 8
• No 6
• No 10

Question 4: As per NEC, minimum ........................ size wire is required for overhead spas up to 50 ft.

• No 8
• No 10
• No 6

NEC Reference: NEC 225.6(A)

Question 5: If the service entrance current transformer has a turns ratio of 200:5. If the primary of  transformer has a current of a 100 amp what is its secondary current in amperes?

• 5 amps
• 10 amps
• 2.5 amps

Question 6: The standby power plant should be capable of delivering the full power within ............... sec of the general power failure.

• 60 sec
• 120 sec
• 90 sec
• 75 sec

Question 7: The emergency power plant, once started after a loss of normal power, must continue to run at least 60 minutes after the power is re-established in a hospital.

• True
• False

Question 8: The power factor of a under excited synchronous motor is always.................

• unity
• leading
• lagging

Question 9: Which of the following motor is most suitable for timing and signalling devices?

• reluctance motor
• D.C Series motor
• linear motor

Question 10: Regulating transformers in power system are used in power system to control ............................

• power factor
• load flow
• voltage

Question 11: What is unique about the speed of a synchronous motor compared to an induction motor?

• It runs above synchronous speed
• It runs at exactly synchronous speed with no slip
• It runs below synchronous speed like an induction motor
• Speed varies continuously with load

Question 12: A 4-pole motor is operated on a 60 Hz supply. What is the synchronous speed?

• 900 RPM
• 1200 RPM
• 1800 RPM
• 3600 RPM

Question 13: A 3-phase induction motor .............

• Needs a starting capacitor to start
• Is self-starting due to the rotating magnetic field
• Cannot start under load — it must start at no load
• Requires a manually operated starting switch

Question 14: Why does a single-phase induction motor need a starting winding or capacitor to start?

• Because single-phase power has lower voltage
• Because the single-phase supply creates a pulsating field that cannot self-start
• Because single-phase motors are always DC motors
• Because single-phase motors have too many poles

Question 15: When multiple grounding electrodes are present at a building, what does NEC 250.50 require?

• Only the best one needs to be connected to the panel
• All grounding electrodes must be bonded together
• Each electrode connects separately to the panel
• Only ground rods need to be connected to each other

NEC Reference: NEC 250.50

Question 16: For a metal water pipe to be used as a grounding electrode, how much of the pipe must be in contact with the earth?

• At least 4 feet
• At least 6 feet
• At least 10 feet
• At least 20 feet

NEC Reference: NEC 250.52(A)(1)

Question 17: A concrete-encased grounding electrode (Ufer ground) uses at least how many feet of reinforcing steel bar?

• 8 feet
• 10 feet
• 20 feet
• 25 feet

NEC Reference: NEC 250.52(A)(3)

Question 18: What is the function of the main bonding jumper at the service entrance?

• It connects the hot wire to the meter
• It connects the neutral to the EGC at the service entrance
• It bonds all branch circuits together
• It provides a path from the panel to the ground rod only

NEC Reference: NEC 250.28

Question 19: What is the purpose of an equipment bonding jumper?

• To bond the neutral and hot conductors in a sub-panel
• To ensure continuity of the equipment grounding conductor path
• To increase the voltage of the circuit
• To connect two separate services together

NEC Reference: NEC 250.102

Question 20: Emergency electrical systems must be tested .............

• Only when the building owner requests it
• Periodically to verify correct operation when normal power fails
• Only during the initial installation inspection
• Emergency systems do not need testing once installed

NEC Reference: NEC 700.3(B)

Question 21: For how long must emergency lighting unit equipment (battery packs) remain on after normal power fails?

• 30 minutes
• 60 minutes
• 90 minutes (1.5 hours)
• 4 hours

NEC Reference: NEC 700.12(F)(1)

Question 22: An over-excited synchronous motor operates with a power factor that is .............

• Lagging
• Leading
• Unity (1.0) always
• Zero always

Question 23: Which of the following locations in a dwelling unit requires GFCI protection for 15- and 20-ampere receptacles?

• Only in the bathroom
• Only in the kitchen
• In bathrooms, garages, outdoors, kitchens, basements, and crawl spaces
• Only in rooms that have plumbing

NEC Reference: NEC 210.8(A)

Question 24: According to NEC 210.12(A), where are arc fault circuit interrupters (AFCI) required in a dwelling unit?

• Only in bedroom circuits
• Only where GFCI is not installed
• All 15- and 20-ampere, 120-volt circuits in all areas of the dwelling
• Only in kitchens and dining areas

NEC Reference: NEC 210.12(A)

Question 25: When measuring the winding resistance of a motor or transformer with an ohmmeter, what must be done first?

• Set the motor to its lowest speed first
• De-energize and turn off all power to the equipment
• Connect the ohmmeter while the motor is running
• Measure through the motor nameplate terminals only

Question 26: What instrument is used to test the insulation quality of motor windings?

• A standard multimeter set to resistance
• A megohmmeter (megger)
• A clamp-on ammeter
• An oscilloscope

Question 27: A digital multimeter (DMM) can measure which of the following quantities?

• Voltage only
• Voltage and current only
• Voltage, current, and resistance
• Power (watts) only

Question 28: What is the main advantage of using a clamp-on ammeter to measure motor current?

• It measures both AC and DC with the same accuracy
• It measures current without breaking the circuit
• It is cheaper than a standard ammeter
• It reads in milliamperes only

Question 29: A built-in thermal protector inside a motor will open the circuit when .............

• The motor speed drops below 75% of rated speed
• The motor winding temperature becomes dangerously high
• The supply voltage drops 10% below rated
• The motor current exceeds its full-load rating by 10%

Question 30: According to NEC Article 100, what is the "service point"?

• The main circuit breaker in the service panel
• The point of connection between the utility and the premises wiring
• The kilowatt-hour meter on the outside of the building
• The first junction box inside the building

NEC Reference: NEC 100