NCCER Electrical Level 2 – Control Systems and Fundamental Concepts (Module 26211-23) Practice Test

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• What is an advantage of solid-state control in electrical systems?
• Alarm contacts are sometimes used with machines that are associated with continuous processing, and are used to signal _____?
• What effect does energizing a relay coil have on the connected load side of the circuit?
• In a control circuit, what is the typical purpose of a bridging wire?
• What is the function of a control transformer in control circuits?
• How does a limit switch function in a control system?
• Melting alloy and bimetallic overload relays are designed so that when current exceeds the designated capacity, it melts an alloy solder pot and ______?
• In a control circuit, what is the purpose of a jumper or bridging wire?
• Which statement best describes the role of labeling and color coding in control wiring?
• How do pushbuttons differ from selector switches in control circuits?
• In a series circuit, what happens if one component opens?
• What is a timer relay and what are common types used in control circuits?
• What is the purpose of a pilot relay in control circuits?
• A diamond symbol with PL indicates which device?
• Lighting contactors are frequently controlled by a two-wire pilot device such as:
• What do Kirchhoff's voltage and current laws state?
• What is the primary purpose of a limit switch in a machine control system?
• Which device is typically actuated by a mechanical plunger or lever in industrial automation?
• What is the standard frequency of North American electrical power, and what effect does it have on AC motor control?
• A _____ is sometimes required to indicate when a motor has stopped due to an overload trip?
• How are control power and line power typically wired in a panel?
• Which statement best differentiates a proximity sensor from a limit switch?
• What is the basic difference between a magnetic (proximity) switch and a temperature switch in control systems?
• Contacts that are together when the relay is de-energized are normally closed.
• Which components are typically found in a motor starter assembly?
• What is a soft-start device and why is it used?
• Contractors are used to only MAKE and never BREAK the circuit to high-current, non-motor loads.
• What does 'neutral' signify in single-phase control systems?
• What is an emergency stop (E-stop) device and how should it be wired in a control circuit?
• What components define a start-stop station and how does it operate?
• Which statement best describes the function of an interlock in a control circuit?
• What is the purpose of a pilot light in a control circuit?
• How do you calculate electrical power in a DC circuit?
• Normally open (NO) contacts are defined as:
• In a bimetallic overload relay, what causes the bimetallic strip to spring away and open the motor control circuit when current exceeds rating?
• Which statement correctly maps the symbol to the device?
• What type of interlocking is used in a magnetic reversing starter to prevent energizing both coils at once?
• What happens when a fuse blows or a circuit breaker trips in a control circuit?
• In a relay, energizing the coil causes which component to move?
• What is a proximity sensor and how is it used in industrial control?
• Which statement best describes the role of PLC input modules?
• What symbol is used to denote low voltage in general electrical diagrams?
• Which statement best describes how lighting contactors differ from standard contactors?
• What is voltage drop and why is it important in wiring calculations?
• What is the function of a limit switch in control circuits?
• Which instrument would you use to measure current in a control circuit and what setting would you use?
• If a control circuit coil has a resistance of 50 ohms and is supplied by 120 V, what is the coil current?
• These overload devices are designed to respond to the heat produced by what in the motor?
• Increasing the armature spring force or magnet gap in a relay results in higher pull-in voltage or current values and higher drop-out values. Choose the correct action that causes this change.
• Why is lockout/tagout (LOTO) important in electrical maintenance?
• The diamond symbol with PL stands for which device?
• Which device is commonly used to manually start or stop a circuit in a control panel?
• How do fuses and circuit breakers differ in protecting electrical circuits?
• What is the purpose of an equipment grounding conductor (EGC) in a circuit?
• An overload relay protects a motor and its related circuits from overloads.
• In addition to protecting operators, isolating control circuits from power circuits also helps with what?
• Describe a basic start-stop motor control circuit using a normally open start pushbutton, a normally closed stop pushbutton, and a holding contact.
• Why must standard motor control contacts be derated if used to control filament-type lamps?
• Which statement is true about control power in relation to line power?
• All of the following are typical solid-state relay control circuits except; Power transistors for DC loads, Power transistors for AC loads, Triac-controlled AC relays, and Reed-controlled AC relays?
• What do NO and NC indicate in pushbutton contacts?
• In a parallel circuit, how is voltage and current distributed?
• How do normally open and normally closed contacts differ in state when the control coil is de-energized?
• True or False: Enclosures for low-voltage lighting and remote-control switching should be placed in areas where no one can get to them to avoid tampering with them?
• Which of the following statements about modern protective relays is accurate?
• Increasing the armature spring force or magnet gap in a relay results in higher pull-in voltage or current values and higher drop-out values. What action is described?
• How does a mechanical interlock prevent two incompatible operations from occurring in sequence?
• Relays are commonly used in the control circuits of all of the following except
• Lockout/tagout is important in maintenance because it prevents unexpected energization and protects workers from injury.
• In a relay, what does a normally open contact do when the coil is energized?
• In motor protection circuits, the primary role of a control relay is to amplify a signal and switch a low-current circuit.
• Many electrical protective relays installed in modern power systems include_____?
• Outline a basic troubleshooting approach for a dead motor starter in a control circuit.
• Fuses are not the best choice to provide motor overload protection because of the high inrush current when starting.
• Power factor is defined as the ratio of real power to apparent power. Which statement best describes its significance in electrical systems with inductive loads?
• What is the primary role of control wiring in a motor control circuit?
• Which relays use a magnetic field to transfer signals via a magnetized element and isolation?
• Which equation correctly relates voltage, current, and resistance according to Ohm's Law?
• Which statement defines Kirchhoff's current law?
• What is short circuit protection and how is it achieved in control circuits?
• An opto-isolated relay uses _____ to control the relay?
• What is the function of a contactor in a motor control circuit?
• Which statement best describes the function of pilot lights in control circuits?
• What is the difference between normally open and normally closed contacts in a control circuit?
• What basic measurements would you perform with a digital multimeter on a control circuit to diagnose a problem?
• What is the role of a relay coil in a control circuit?
• How would you test a relay coil for proper operation?
• True or False: Standard overload relay contacts open under normal conditions and close when the relay trips.
• What information can you read from a control schematic?
• What is arc-flash awareness and how does it influence electrical work practices?
• To reverse the rotation of a three-phase motor, which lead changes are specified?
• What distinguishes a momentary pushbutton from a maintained pushbutton in control circuits?
• What is the primary purpose of a bimetallic overload relay?
• What is the purpose of an isolation device in a control panel?
• What is the correct statement about normally open and normally closed contacts in safety interlocks?
• After identifying a suspect relay, what is a prudent next step in testing the control circuit?
• Which statement best describes the difference between a control circuit and a power circuit?
• What is the purpose of PLC input/output modules?
• What is the purpose of a grounding electrode system in industrial electrical installations?
• The overload relay is the heart of motor protection and may be used instead of overcurrent protective equipment.
• Why is color coding and labeling important in control wiring?
• What is the general purpose of the NEC in electrical installations?
• True or False: Overload relays are not classified; there are only a few categories.
• How does a hard-wired control circuit differ from PLC-based control?
• A controller's output interface is often provided by a device with no moving parts to control a higher-power load.
• In a series circuit, how does current flow and how are voltages distributed?
• The claim that a contactor action is mechanically held because it depends on current through the coil is true or false?
• A typical motor start-stop control uses which components?
• Why is a control transformer used in low-voltage control circuits?
• True or False: Manufacturers may require that high-voltage portions for lighting enclosures be mounted in the upper right hand corner of an enclosure to conform with NEC requirements to keep low and high-voltage conductors separate.
• The diamond symbol with a T denotes which device?
• A contactor is best described as a device used to switch the motor power circuit on and off under control of a low-voltage coil.
• True or False: Overload relays have many classifications; a few examples are Thermal, Magnetic, energy-saving, normally open (NO) relays, normally closed (NC) relays.
• Which two safety practices are basic when working on electrical control circuits?
• How is current calculated in a three-phase circuit when line voltage V_LL and power P are known (PF = 1)?
• What is the effect of energizing the coil on the armature's position in a relay?
• Normally closed (NC) contacts are defined as:
• What is a start interlock in a multi-motor system?
• Dual-element or time-delay fuses can provide motor overload protection but have the disadvantage of ______?
• What is the typical purpose of a selector switch in a control circuit?
• Which component provides overload protection by tripping when current is too high?
• What is a pushbutton interlock and provide an example of its use.
• How should ladder logic be interpreted in PLC programming?
• Which device is immune to temperature changes?
• What constitutes a functional test for a motor control circuit after wiring changes?
• How do a short circuit and an overload differ in a circuit?
• In a three-phase system, with PF = 1, which is the correct expression for current I in terms of total power P and line-to-line voltage V_LL?
• What factor is most important in selecting conductor size for a control circuit?
• Mechanically held relays are used where the hum of electrically held devices is objectionable, such as:
• Which statement about ladder logic is accurate?
• Referring to 2.4.0 Table 2A, what is the probable cause if the symptom is "Failure of equipment to start with contactor closed"?
• Which statement is NOT an advantage of solid-state control?
• What is a pilot light and what is its typical use in control circuits?
• Interlocking prevents both direction contactors from energizing at the same time.
• In a conventional contactor, current flow through the coil creates a _____ to seal in the armature and maintain the contacts in a switched position.
• What is the difference between grounding and bonding in electrical systems?
• True or False: Enclosures for low-voltage lighting and remote-control switching should be placed in areas where no one can get to them to avoid tampering with them.
• In a basic forward-reverse motor control circuit, which arrangement provides interlocking to prevent simultaneous energization of forward and reverse?
• Shading coils are used with AC relays to prevent:
• What is the purpose of a snubber across a relay coil?
• Which statement is true about normally open contacts?
• True or False: In overload relays, contacts open under normal conditions and close when the relay trips.
• Emergency lighting circuits often use which type of relay so lamps can light instantly after a main power failure?
• Which statement best describes the basic difference between a magnetic proximity switch and a temperature switch?
• Which protective device can be reset after tripping, rather than replaced, and is used to interrupt excess current?
• What is fault analysis in control circuits?
• When low-voltage and high-voltage cables run in parallel, they should be separated by at least how many inches?
• What is the purpose of fuses and circuit breakers in control circuits?
• How does applying AC to a coil produce motion in a relay?
• Lighting contactors are designed by ampere ratings; which rating is not among the typical sizes listed?
• The heater element of a bimetallic overload relay is sized to half of the full-load current.
• Which expression correctly defines electrical power in a DC circuit?
• What components comprise a magnetic reversing starter?
• Which device provides a visual indication of circuit status in a control panel?
• In a forward-reverse motor control circuit, what is the role of an emergency stop?
• A motor starter typically uses a device designed to handle higher current than a standard relay.
• What is a control loop and how is feedback used?
• Which statement correctly describes reversing the direction of a three-phase squirrel-cage motor?
• Which statement correctly defines Kirchhoff's voltage law?
• Transformers designed for use on remote control switching systems supply what power?
• In a series circuit, which statement is true?
• True or False: Overload relays have many classifications; a few examples are Thermal, Magnetic, energy-saving, normally open (NO) relays, normally closed (NC) relays.
• Which device is commonly used to switch a motor's power circuit in an electrical control system?
• Referring to a control circuit, what device is used to control the operation of a number of different loads?
• Which statement is true about normally closed contacts?
• True or False: Remote control switching systems employ a split low-voltage coil to move the line voltage contact armature to the ON (latched) position.
• When trying to use a small pump to deliver lubrication to bearings of a motor for a set period of time, a _____ may be used?
• Most overload relays used on modern motor starters are magnetically operated and consist of two strips of metal welded together.
• Which statement best describes the function of a motor starter coil energization test during troubleshooting?
• In a basic ladder logic representation, what is the function of a contact associated with a coil?
• What is a ground fault and how is it normally detected?
• In a control circuit, a timing relay provides operation after a preset delay or at a set interval. Which option best describes this behavior?
• What is the purpose of a motor overload device in a motor control circuit?
• What is the difference between a voltmeter and an ammeter in control circuits?
• True or False: Enclosures for low-voltage lighting and remote-control switching should be placed in areas where no one can get to them to avoid tampering with them.
• Ohm's law relates voltage, current, and resistance. Which equation expresses Ohm's law?
• What is a holding contact in a control circuit and why is it used?
• Which device is typically used to stop operations quickly in a control system during an emergency?
• What is the primary purpose of a contactor in electrical control circuits?
• In a control panel, what is the purpose of a transformer?
• What is the function of a normally closed auxiliary contact in a control circuit when the associated device is energized?
• Magnetic overload relays react only to current excess and are not affected by ______?
• In a magnetic contactor, which part is attracted or picked up by the coil when energized?
• A thermal overload relay monitors current; if current exceeds rating due to overload, it trips the circuit; resets after cooling.
• A solid-state relay is commonly used for PLC I/O to allow the controller to be reprogrammed without rewiring.
• In sensor outputs, how do NO and NC differ when activated?
• Which component is used to provide overload protection for a motor and is often paired with a contactor?
• What distinguishes open-loop control from closed-loop control?
• In diagnosing a control circuit with multiple relays, why is it important to verify coil energization before testing contacts?
• In a relay control circuit, what happens to a normally open contact when its controlling coil energizes?
• True or False: Manufacturers may require that high-voltage portions for lighting enclosures be mounted in the upper right hand corner of an enclosure to conform with NEC requirements to keep low and high-voltage conductors separate.
• What happens to a normally closed contact when its coil is energized?
• If you need a sensor output that energizes when detection occurs, which type should you use?
• When diagnosing a control circuit with multiple relays, what is a systematic approach to determine the faulty component?
• What is the purpose of a holding contact in a start-stop motor control circuit?
• In a parallel circuit, what happens when one branch is removed?
• True or False: Manufacturers may require that high-voltage portions for lighting enclosures be mounted in the upper right hand corner of an enclosure to conform with the NEC requirements to keep low and high-voltage conductors separate?
• How do thermal overloads protect motors and what characteristic can trigger them?
• True or False: Standard overload relay contacts open under normal conditions and close when the relay trips.
• What is a VFD and what control concept does it illustrate?
• What do electrical and mechanical interlocks prevent in a magnetic reversing starter?
• What is one key benefit of performing a systematic test of a motor control circuit after changes?
• In remote control switching circuits in certain applications, what provides the low voltage?
• Which statement describes one or more advantages of low voltage remote control relay systems?
• How do normally open and normally closed contacts contribute to safety interlocks?
• Common color conventions for hot, neutral, and ground conductors in a typical North American control circuit?
• What is the function of a terminal block in a control panel?
• What are common methods by which a limit switch is actuated in industrial equipment?
• In a three-wire control circuit, which component often supplies the control power?
• What is a common first step in troubleshooting a malfunctioning motor control circuit?
• Which statement describes the difference between two-wire and three-wire control circuits?
• Normally open contacts are open when the relay coil is de-energized.
• Conditions of a motor overload may be caused by which of the following?
• In a bimetallic overload relay, what physical change causes the strip to trip when overheated?
• Which statement best describes the difference between a control relay and a contactor?
• In a parallel circuit, what is true about the voltage across each component?
• In electrical drawings, what does a relay coil symbol indicate?
• What term describes the combination used to reverse motor direction?
• Which devices are typically operated by a control circuit?
• What is redundancy in control systems and why is it important?
• In a control loop, what is the role of feedback?
• What is an overload relay and why is it used in motor circuits?
• In a series circuit, which statement is true about the current through components?
• What happens to a normally open contact when its coil is energized?
• This type of solid-state relay uses a magnetic field to isolate the control circuit from the load?
• True or False: Remote control switching systems use a split low-voltage coil to move the line voltage contact armature to the ON (latched) position.
• True or False: Remote control switching systems employ a split low-voltage coil to move the line voltage contact armature to the ON (latched) position.
• What is the difference between an on-delay timer and an off-delay timer?
• In a motor starter assembly, which device switches the motor circuit on and off?
• Which arrangement describes a fused disconnect protecting a circuit from overloads?
• Which device provides a visual indication that a circuit is energized?
• How does a solid-state relay differ from a mechanical relay in control circuits?
• Which statement best describes the effect of a low power factor on system performance?
• A pneumatic timer or timing relay is similar to a control relay, except that it contains contacts that are designed to operate_____?
• Under NEC conditions, what type of conductors may be run in open spaces above ceilings and through wall partitions without additional protection?
• Which device detects imbalance between hot and neutral currents and trips to prevent shock?
• A fused disconnect provides a means to disconnect power and protect the circuit with fuses against overload or short circuits.