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Question 1. Which of the following is the primary purpose of a lockout/tagout (LOTO) device? A) To indicate that a circuit is energized B) To physically prevent the release of stored energy C) To provide a visual warning only D) To ground the equipment Answer: B Explanation: LOTO devices are applied to isolate and secure energy sources, physically preventing the equipment from being re-energized until the lock is removed. Question 2. When selecting personal protective equipment (PPE) for arc‑flash work, which class of clothing is required for a minimum incident energy of 8 cal/cm²? A) Class 1 (25 cal/cm²) B) Class 2 (8 cal/cm²) C) Class 3 (4 cal/cm²) D) No special clothing is needed Answer: B Explanation: Class 2 arc‑flash clothing is rated for a minimum of 8 cal/cm², providing adequate protection for that exposure level. Question 3. Which tool is specifically designed to remove the insulation from a single conductor without damaging adjacent wires? A) Wire stripper B) Crimping tool C) Knock‑out punch D) Diagonal cutter Answer: A
Explanation: A wire stripper has calibrated holes that strip insulation from a single conductor while leaving neighboring conductors untouched. Question 4. For an electrical fire involving energized equipment, which type of fire extinguisher is appropriate? A) Class A B) Class B C) Class C D) Class D Answer: C Explanation: Class C extinguishers are designed for fires involving energized electrical equipment and are non‑conductive. Question 5. On a digital multimeter (DMM), which setting should be selected to measure the resistance of a component? A) V Ω A B) Continuity C) Ω (Ohms) D) mA Answer: C Explanation: The Ω symbol on a DMM indicates the resistance measurement mode. Question 6. A circuit contains a 12 V source and a resistor of 4 Ω. What is the current flowing through the resistor? A) 2 A B) 3 A C) 0.33 A D) 48 A
Answer: A Explanation: In a parallel configuration, all branches share the same voltage equal to the source voltage. Question 10. A 150 W lamp operates on a 120 V circuit. What is its current draw? A) 0.8 A B) 1.25 A C) 12 A D) 18 A Answer: B Explanation: I = P / V = 150 W / 120 V = 1.25 A. Question 11. Which ANSI symbol represents a single‑pole, single‑throw (SPST) switch? A) ‖—| B) —|—| C) ──| D) —⏚— Answer: C Explanation: The ANSI symbol for an SPST switch is a single break in the line (─│). Question 12. A resistor is marked with the color code red‑violet‑brown. What is its nominal resistance? A) 2.7 kΩ B) 270 Ω C) 27 Ω D) 2.7 Ω
Answer: B Explanation: Red (2), violet (7), multiplier brown (×10) → 27 × 10 = 270 Ω. Question 13. Which type of circuit protector reacts primarily to over‑current caused by short circuits? A) Thermal fuse B) Magnetic circuit breaker C) Slow‑blow fuse D) Ground‑fault interrupter Answer: B Explanation: Magnetic breakers respond quickly to the high instantaneous currents typical of short circuits. Question 14. In a voltage divider consisting of two equal resistors, the voltage at the midpoint is: A) 0 V B) ¼ of source voltage C) ½ of source voltage D) Equal to source voltage Answer: C Explanation: Two equal resistors split the source voltage equally, giving half at the midpoint. Question 15. Which component converts a high‑current AC line voltage to a low‑current control voltage? A) Relay B) Contactor C) Transformer D) Solenoid
Question 19. A push‑button labeled “STOP” is typically wired as a: A) Normally Open (NO) momentary contact B) Normally Closed (NC) momentary contact C) Latching contact D) Double‑throw switch Answer: B Explanation: STOP buttons are usually NC so that loss of the button (or a fault) opens the circuit and stops the machine. Question 20. In ladder logic, the two vertical lines represent: A) Power rails (L1 and L2) B) Ground and neutral C) Input and output modules D) Relay coils Answer: A Explanation: The vertical lines are the main power rails (often called line and neutral or L1/L2). Question 21. Which logic gate is equivalent to two switches wired in series? A) OR B) AND C) NOT D) NAND Answer: B Explanation: Series switches require both to be closed for current to flow, representing an AND function.
Question 22. A fault in an electrical system that results in a very low resistance path to ground is called a: A) Open circuit B) Short circuit C) High‑impedance fault D) Overload Answer: B Explanation: A short circuit creates a low‑resistance path, causing excessive current flow. Question 23. When using a DMM to locate a voltage drop, the first step is to: A) Set the meter to continuity mode B) Verify the circuit is de‑energized C) Measure voltage at the source terminals D) Measure resistance of each component Answer: C Explanation: Measuring at the source establishes a reference point for subsequent voltage drop measurements. Question 24. Which component is typically tested out‑of‑circuit by applying a known voltage and measuring coil resistance? A) Fuse B) Circuit breaker C) Relay coil D) Indicator light Answer: C Explanation: Relay coils are tested by applying voltage and checking that the measured resistance matches the coil’s specification.
Explanation: Magnetic mechanisms react instantly to high fault currents, while thermal elements trip on sustained overloads. Question 28. In a three‑phase Y‑connected system, the line‑to‑neutral voltage is 120 V. What is the line‑to‑line voltage? A) 120 V B) 208 V C) 240 V D) 415 V Answer: B Explanation: Line‑to‑line voltage = √ 3 × line‑to‑neutral → √ 3 × 120 V ≈ 208 V. Question 29. Which type of switch changes the circuit path without interrupting the current flow? A) SPST B) DPDT C) Rotary selector (maintained) D) Momentary push‑button Answer: C Explanation: A rotary selector can change connections while maintaining power, often used for mode selection without breaking the circuit. Question 30. A color‑coded resistor reads brown‑black‑red‑gold. What is its tolerance? A) ±1 % B) ±2 % C) ±5 % D) ±10 % Answer: C
Explanation: Gold indicates a tolerance of ±5 %. Question 31. Which instrument is used to verify that a circuit is truly de‑energized before work begins? A) Clamp‑on ammeter B) Voltage tester (non‑contact) C) Megohmmeter D) Oscilloscope Answer: B Explanation: A non‑contact voltage tester can quickly confirm the absence of voltage. Question 32. In a series‑parallel circuit, the method to simplify the network is: A) Apply Thevenin’s theorem only B) Reduce all series groups first, then parallel groups, repeating as needed C) Convert all resistors to their admittance values D) Use only Kirchhoff’s laws without simplification Answer: B Explanation: Systematically reducing series and parallel groups yields an equivalent resistance. Question 33. The purpose of a pilot light labeled “FAULT” is to: A) Indicate that the machine is running B) Show that a safety interlock is active C) Illuminate when a fault condition exists in the control circuit D) Provide illumination for the operator Answer: C Explanation: A fault pilot light is wired to illuminate only when a fault condition is detected.
Question 37. In a ladder diagram, a normally closed (NC) contact placed before a coil will cause the coil to be energized when: A) The contact is open B) The contact is closed C) The contact is energized D) The contact is de‑energized Answer: A Explanation: An NC contact breaks the circuit when it opens; thus the coil receives power when the NC contact is open. Question 38. Which measurement mode on a DMM is best for detecting a broken wire in a circuit? A) Voltage AC B) Resistance (Ω) C) Continuity beep D) Current DC Answer: C Explanation: The continuity mode emits an audible tone when a low‑resistance path exists, indicating continuity. Question 39. A 240 V, 10 A circuit breaker is protecting a motor. What is the maximum power the circuit can safely deliver? A) 2.4 kW B) 24 kW C) 240 W D) 1.2 kW Answer: A
Explanation: Power = V × I = 240 V × 10 A = 2,400 W = 2.4 kW. Question 40. Which of the following is NOT a typical function of a selector switch? A) Change operating modes B) Provide a momentary start command C) Select between multiple power sources D) Enable or disable a specific circuit Answer: B Explanation: Selector switches are maintained (stay in position) rather than momentary. Question 41. The primary purpose of a ground‑fault circuit interrupter (GFCI) is to: A) Protect against over‑current B) Detect and disconnect leakage currents to ground C) Provide surge protection D) Isolate neutral conductors Answer: B Explanation: GFCIs monitor imbalance between hot and neutral currents and trip when leakage to ground exceeds a threshold. Question 42. In a three‑wire motor circuit (L1‑L2‑L3), which wire typically serves as the protective earth? A) L B) L C) L D) None; a separate green‑yellow earth conductor is used Answer: D
Question 46. Which of the following is a characteristic of a magnetic contactor’s auxiliary contacts? A) They carry the main motor current B) They are used for control and signaling, not for load switching C) They provide overload protection D) They are only used in DC circuits Answer: B Explanation: Auxiliary contacts are low‑current contacts used for control logic, not for carrying the main load. Question 47. When performing a voltage drop test on a long cable run, the most common cause of excessive drop is: A) High resistance due to undersized conductors B) Low source voltage C) Excessive grounding D) Use of insulated conductors Answer: A Explanation: Undersized conductors have higher resistance, leading to larger voltage drops over distance. Question 48. A “normally open” (NO) push‑button is used to start a motor. What happens when the button is released? A) The motor continues to run B) The motor stops immediately C) The motor runs at reduced speed D) The motor runs in reverse Answer: B
Explanation: An NO start button provides a momentary contact; releasing it opens the circuit, stopping the motor unless latched. Question 49. Which of the following statements about a soft‑starter is false? A) It reduces mechanical stress on the motor B) It eliminates the need for a protective overload relay C) It controls the voltage applied during start‑up D) It can be used with three‑phase induction motors Answer: B Explanation: A soft‑starter does not replace overload protection; an overload relay is still required to protect the motor from sustained overcurrent. Question 50. In a ladder diagram, a rung that contains only a coil without any contacts is called a: A) Seal‑in rung B) Latching rung C) Output rung D) Input rung Answer: C Explanation: A rung that only energizes a coil (output device) is termed an output rung. Question 51. Which IEC symbol represents a normally closed (NC) contact? A) ⎕—| B) —|—| C) —| D) ⎕—⎕ Answer: C
Answer: A Explanation: Magnetic overload relays sense over‑current and open the circuit after a short, thermal‑based delay. Question 55. In a three‑phase delta‑connected motor, the line voltage is equal to: A) Phase voltage B) √3 × phase voltage C) Phase voltage / √ D) 2 × phase voltage Answer: A Explanation: In a delta connection, line voltage equals the phase voltage across each winding. Question 56. Which tool is used to verify that a circuit breaker has successfully tripped? A) Voltage tester B) Clamp‑on ammeter C) Torque wrench D) Insulation resistance tester Answer: B Explanation: A clamp‑on ammeter can confirm that current is zero, indicating the breaker has opened. Question 57. A control relay coil is rated at 120 V DC, 0.5 A. What is its coil resistance? A) 60 Ω B) 240 Ω C) 0.004 Ω D) 120 Ω Answer: A
Explanation: R = V / I = 120 V / 0.5 A = 240 Ω (correction: 120/0.5 = 240 Ω, so answer B). Question 58. Which of the following is the correct method to verify zero energy before beginning work on a de‑energized panel? A) Visual inspection only B) Apply a voltage detector and confirm no voltage, then lock out the source C) Touch the live parts with a hand D) Rely on the lockout tag alone Answer: B Explanation: Using a voltage detector confirms the absence of voltage; lockout/tagout then secures the source. Question 59. What is the purpose of a “seal‑in” (or “latching”) circuit in motor control? A) To provide a temporary start pulse only B) To keep the motor running after the start button is released C) To protect the motor from overloads D) To reverse motor direction Answer: B Explanation: A seal‑in circuit uses a normally closed contact that holds the starter coil energized after the start button is released. Question 60. In a series circuit of three resistors (R1=10 Ω, R2=20 Ω, R3=30 Ω) connected to a 60 V source, what is the voltage across R2? A) 10 V B) 12 V C) 20 V D) 30 V
