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Practice Exam
Question 1. What is the relationship between voltage, current, and resistance in Ohm’s Law? A) V = I + R B) V = I × R C) V = I ÷ R D) V = R ÷ I Answer: B Explanation: Ohm’s Law states that voltage (V) equals current (I) multiplied by resistance (R). Question 2. In a single‑phase residential supply, what is the typical frequency in the United States? A) 50 Hz B) 60 Hz C) 400 Hz D) 100 Hz Answer: B Explanation: North American residential AC power operates at 60 Hz. Question 3. Which formula correctly calculates electrical power in a resistive load? A) P = V / I B) P = V × I C) P = I² / R D) P = V² / I Answer: B Explanation: Power (P) equals voltage (V) multiplied by current (I) for any load.
Practice Exam
Question 4. A heater rated at 1500 W is connected to a 120 V circuit. What current does it draw? A) 5 A B) 10 A C) 12.5 A D) 15 A Answer: B Explanation: I = P ÷ V = 1500 W ÷ 120 V = 12.5 A (rounded to 12.5 A, answer choice B is the closest standard rating of 12.5 A; however, the correct calculation yields 12.5 A, which matches option C. Correct answer: C). Question 5. When two identical resistors are connected in series, the total resistance is: A) Half the resistance of one resistor B) Equal to one resistor C) Twice the resistance of one resistor D) The square of one resistor’s value Answer: C Explanation: Series resistance adds, so R_total = R + R = 2R. Question 6. In a parallel circuit, the voltage across each branch is: A) The sum of branch voltages B) Equal to the source voltage C) Half the source voltage D) Determined by the branch with the highest resistance Answer: B
Practice Exam
Answer: A Explanation: A thermal fuse opens the circuit permanently if temperature exceeds a limit. Question 10. What is the main purpose of a Ground Fault Circuit Interrupter (GFCI) in a kitchen outlet? A) To protect against short circuits B) To limit inrush current C) To detect ground‑fault currents and disconnect the circuit D) To regulate voltage Answer: C Explanation: GFCIs monitor imbalance between hot and neutral and trip when a ground fault is detected. Question 11. Which NEC article primarily addresses the grounding of residential appliances? A) Article 210 B) Article 250 C) Article 300 D) Article 430 Answer: B Explanation: Article 250 of the NEC covers grounding and bonding requirements. Question 12. A 240 V dryer uses a 30 A circuit. What is the minimum AWG copper conductor size required by the NEC (assuming 75 °C rating)? A) 12 AWG B) 10 AWG
Practice Exam
C) 8 AWG
D) 6 AWG
Answer: C Explanation: For 30 A, the NEC requires at least 8 AWG copper conductors (75 °C column). Question 13. When measuring the resistance of a heating element with a multimeter, the reading should be: A) Zero ohms B) Infinite ohms C) Within the manufacturer’s specified range D) Equal to the line voltage Answer: C Explanation: The measured resistance must match the element’s spec; zero indicates a short, infinite indicates an open. Question 14. Which type of motor is most common in residential washing machines? A) Shaded‑pole motor B) Universal motor C) PSC motor D) Brushless DC motor Answer: B Explanation: Universal motors can run on AC or DC and are used for high‑speed wash/drain functions. Question 15. A refrigerator’s defrost heater is controlled by a thermostat that closes at: A) Low temperature
Practice Exam
Question 18. Which component in a dishwasher prevents the motor from running when the door is open? A) Thermal fuse B) Door interlock switch C) Timer relay D) Flow sensor Answer: B Explanation: The door interlock switch breaks the motor circuit when the door is not fully closed. Question 19. A 120 V incandescent lamp draws 0.5 A. What is its resistance? A) 60 Ω B) 240 Ω C) 480 Ω D) 120 Ω Answer: B Explanation: R = V ÷ I = 120 V ÷ 0.5 A = 240 Ω. Question 20. When troubleshooting a faulty oven, which test would confirm a broken heating element? A) Measure voltage across the element while the oven is on B) Measure continuity across the element with power off C) Measure current draw of the element while on D) Check for audible click from the thermostat Answer: B
Practice Exam
Explanation: Continuity testing with power removed verifies whether the element is open (broken). Question 21. What does a “split‑phase” residential service provide? A) Two 120 V lines that are 180° out of phase, creating 240 V between them B) Three 120 V lines 120° apart C) A single 240 V line only D) Four 120 V lines in a four‑wire system Answer: A Explanation: Split‑phase uses two 120 V legs opposite in phase, giving 240 V between them. Question 22. Which device protects an appliance’s control board from voltage spikes? A) Thermal fuse B) Metal‑oxide varistor (MOV) C) Ground fault interrupter D) Circuit breaker Answer: B Explanation: An MOV clamps transient over‑voltages, protecting sensitive electronics. Question 23. In a series‑parallel appliance circuit, the total current is determined by: A) Adding the currents of all parallel branches only B) Adding the currents of series elements only C) Summing the branch currents that are in parallel, then adding series currents D) Multiplying the branch currents together Answer: C
Practice Exam
Question 26. Which of the following best describes a “neutral” conductor in a split‑phase system? A) Carries unbalanced current back to the utility transformer center tap B) Is always at ground potential and carries no current C) Is the same as the equipment grounding conductor D) Supplies 240 V to appliances Answer: A Explanation: The neutral provides a return path for the unbalanced load between the two hot legs. Question 27. When using a clamp‑on ammeter on a three‑phase motor, the meter must be placed around: A) Only one phase conductor B) All three phase conductors together C) The neutral only D) The ground conductor Answer: A Explanation: For accurate line current measurement, the clamp must encircle a single phase conductor. Question 28. What is the primary function of a centrifugal switch in a universal motor? A) To reverse motor direction B) To disconnect the start winding at rated speed C) To protect against overload D) To provide a ground path Answer: B
Practice Exam
Explanation: The centrifugal switch opens when the motor reaches a certain speed, removing the start winding from the circuit. Question 29. A dishwasher’s heating element is rated at 1800 W at 120 V. What is its resistance? A) 8 Ω B) 12 Ω C) 20 Ω D) 40 Ω Answer: B Explanation: R = V² ÷ P = (120 V)² ÷ 1800 W = 14400 ÷ 1800 = 8 Ω. (Correct answer is A). Question 30. Which safety device must be installed on a dedicated 240 V dryer circuit in a bathroom? A) GFCI breaker or receptacle B) AFCI breaker only C) Thermistor D) Surge protector Answer: A Explanation: NEC requires GFCI protection for dryer outlets in wet locations such as bathrooms. Question 31. When a motor’s start capacitor fails open, the motor will typically: A) Run at full speed B) Not start or start very slowly C) Run in reverse direction D) Overheat immediately
Practice Exam
C) Clamp‑on ammeter D) Oscilloscope Answer: B Explanation: A megohmmeter applies a high voltage to assess insulation resistance. Question 35. In a refrigerator, a “capillary tube” acts as: A) A mechanical thermostat B) A refrigerant expansion device controlling flow rate C) An electronic sensor for temperature D) A motor starter for the compressor Answer: B Explanation: The capillary tube provides a fixed restriction that meters refrigerant flow into the evaporator. Question 36. When wiring a new electric range, which conductor must be connected to the equipment grounding conductor (EGC)? A) The neutral B) The chassis or metal frame of the range C) The hot leg only D) The control board ground only Answer: B Explanation: The EGC must be bonded to the appliance’s metal chassis for safety. Question 37. A 30‑amp circuit breaker trips repeatedly when a dryer is running. Which is the most probable cause? A) Undersized heating element
Practice Exam
B) Over‑sized wiring C) A shorted heating element or a ground fault D) Incorrect breaker rating (too high) Answer: C Explanation: A repeated trip indicates an overcurrent condition, often due to a shorted element or ground fault. Question 38. Which type of relay contacts are normally closed (NC) when the coil is de‑energized? A) NO (Normally Open) contacts B) NC (Normally Closed) contacts C) SPDT contacts D) DPST contacts Answer: B Explanation: NC contacts are closed in the relay’s resting state and open when the coil is energized. Question 39. In a dishwasher, the “solenoid valve” is used to: A) Heat the water B) Pump water out of the tub C) Control water inlet flow D) Rotate the spray arm Answer: C Explanation: The solenoid valve opens to allow water into the dishwasher during the fill cycle. Question 40. Which of the following best describes a “thermal fuse” in a dryer?
Practice Exam
Question 43. Which NEC requirement applies to the spacing of receptacles in a kitchen countertop? A) No more than 12 ft apart B) No more than 6 ft apart C) Must be within 18 in of the countertop edge D) Must be within 24 in of the sink Answer: B Explanation: NEC 210.52(C) requires receptacles no more than 6 ft apart along the countertop. Question 44. What is the purpose of a “burn‑in” test for a new appliance’s control board? A) To verify mechanical integrity B) To simulate long‑term operation and detect early failures C) To calibrate temperature sensors D) To test grounding continuity Answer: B Explanation: Burn‑in testing runs the board under load to uncover latent defects. Question 45. A 120 V, 60 Hz AC motor has an inductive reactance of 30 Ω and resistance of 10 Ω. What is its impedance magnitude? A) 10 Ω B) 30 Ω C) 31.6 Ω D) 40 Ω Answer: C Explanation: Z = √(R² + X²) = √(10² + 30²) = √(100 + 900) = √1000 ≈ 31.6 Ω.
Practice Exam
Question 46. Which component in a refrigerator’s defrost circuit limits the maximum temperature of the heating element? A) Defrost thermostat B) Temperature sensor C) Control board timer D) Compressor pressure switch Answer: A Explanation: The defrost thermostat opens when the element reaches its set temperature, preventing overheating. Question 47. When a dryer’s drum motor fails open, what symptom will you observe? A) The dryer heats but the drum does not turn B) The dryer turns but does not heat C) Both heating and turning stop D) The dryer makes a loud humming noise Answer: A Explanation: An open motor prevents drum rotation while the heating element can still function. Question 48. A “split‑phase” transformer’s center tap is connected to: A) Ground only B) The neutral conductor of the service panel C) The hot leg of the circuit D) The equipment grounding conductor Answer: B
Practice Exam
Answer: B Explanation: Dryer limit thermostats are commonly rated for 10 A at the appliance’s 240 V supply. Question 52. Which test would verify that a dishwasher’s drain pump is electrically functional? A) Measure voltage at the pump terminals while the cycle runs B) Listen for the pump’s sound during the drain phase C) Check water level sensor resistance D) Verify that the door latch is engaged Answer: A Explanation: Applying voltage measurement confirms the pump receives power during operation. Question 53. A 240 V range uses two heating elements, each rated 2500 W. What is the total current drawn when both are on? A) 10.4 A B) 20.8 A C) 14.6 A D) 21.7 A Answer: B Explanation: Total power = 5000 W; I = P ÷ V = 5000 W ÷ 240 V = 20.8 A. Question 54. Which of the following is the correct order of steps for Lockout/Tagout (LOTO) on a dryer? A) Notify, isolate, test, lock, tag
Practice Exam
B) Identify, isolate, lock, tag, verify de‑energized C) Isolate, lock, tag, test, restore power D) Notify, lock, tag, verify, restore Answer: B Explanation: Proper LOTO: identify energy sources, isolate them, apply lock, apply tag, then verify that the equipment is de‑energized. Question 55. A “PTC” thermistor used as a resettable fuse behaves how when it overheats? A) Its resistance decreases, allowing more current B) Its resistance increases sharply, limiting current C) It opens permanently like a fuse D) It acts as a voltage regulator Answer: B Explanation: PTC thermistors increase resistance dramatically when temperature exceeds a threshold, limiting current. Question 56. Which NEC article governs the use of AFCI protection in kitchen circuits? A) 210. B) 210. C) 210. D) 210. Answer: A Explanation: NEC 210.12 requires AFCI protection for dwelling unit kitchen branch circuits. Question 57. In a refrigerator, the “evaporator fan motor” is typically powered from:
