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CT Fire Alarm practice questions

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Question 1Fire Alarm Systems and Code Requirements

According to NFPA 72, which device is required at the main fire alarm control unit location to alert personnel of a system trouble condition?

  1. A remote annunciator installed only in the fire command center
  2. A telephone dialer that calls the monitoring agency
  3. A visible and audible trouble signal at the control unit and at a constantly attended location Correct answer.
  4. A strobe light mounted above the main entrance

Explanation

NFPA 72 requires trouble signals to be indicated audibly and visibly at the control unit and, where a constantly attended location exists, annunciated there as well. The purpose is to ensure that a degraded system is noticed promptly by someone able to act.

Question 2Fire Alarm Systems and Code Requirements

In a protected premises fire alarm system, what is the primary function of an initiating device circuit?

  1. To provide 24-volt power to door holders
  2. To connect automatic and manual initiating devices to the control unit Correct answer.
  3. To supervise the battery charging circuit
  4. To carry notification appliance power from the panel

Explanation

Initiating device circuits link detectors and manual pull stations to the control unit so alarm signals can be processed. Notification appliance circuits and power circuits serve separate functions and are supervised independently.

Question 3Fire Alarm Systems and Code Requirements

A manual fire alarm pull station must be installed so that its operable portion is located within what height range above the finished floor, per NFPA 72?

  1. 48 to 84 inches
  2. 36 to 60 inches Correct answer.
  3. 24 to 48 inches
  4. 42 to 78 inches

Explanation

NFPA 72 requires the operable portion of manual fire alarm boxes to be mounted between 42 and 48 inches typically, but the widely cited accessible range for pull stations is 36 to 60 inches above the floor per the standard. Always verify against the edition adopted locally.

Question 4Fire Alarm Systems and Code Requirements

Which of the following best describes the purpose of a smoke detector's listed spacing when applied to a smooth ceiling?

  1. It sets the minimum battery backup duration
  2. It defines the maximum circuit length for the detector loop
  3. It provides a design basis for detector placement under defined ceiling and airflow conditions Correct answer.
  4. It guarantees detection of any fire size within the listed area

Explanation

Listed spacing is a design basis developed under specific test conditions for smooth ceilings. Actual layouts must account for ceiling height, configuration, and air movement per NFPA 72.

Question 5Fire Alarm Systems and Code Requirements

What does a supervisory signal indicate on a fire alarm system?

  1. A total loss of primary AC power
  2. An off-normal condition of a system component such as a valve or sprinkler switch Correct answer.
  3. A ground fault on a notification circuit
  4. An actual fire condition requiring immediate evacuation

Explanation

Supervisory signals report off-normal conditions of protected-system components, such as closed valves or low air pressure, that could impair performance. They are distinct from alarm and trouble signals.

Question 6Fire Alarm Systems and Code Requirements

Which NFPA document primarily governs the installation, performance, and maintenance of fire alarm systems?

  1. NFPA 70
  2. NFPA 13
  3. NFPA 72 Correct answer.
  4. NFPA 101

Explanation

NFPA 72 is the National Fire Alarm and Signaling Code and covers design, installation, testing, and maintenance. The other documents address sprinklers, life safety, and electrical wiring respectively.

Question 7Fire Alarm Systems and Code Requirements

A duct smoke detector installed in an HVAC system is primarily intended to do which of the following?

  1. Detect smoke in the air handling system and initiate a supervisory or alarm response Correct answer.
  2. Replace the need for manual pull stations
  3. Serve as a substitute for area smoke detection in the occupied space
  4. Provide early warning of overheating in the duct heater

Explanation

Duct detectors sample air moving through the HVAC system and respond to smoke present in the duct. NFPA 72 does not permit them to substitute for required area detection.

Question 8Fire Alarm Systems and Code Requirements

What is the required function of an end-of-line resistor in a conventional initiating device circuit?

  1. To provide surge protection to the loop
  2. To allow the panel to supervise the circuit wiring for opens and shorts Correct answer.
  3. To limit current to the detectors
  4. To convert AC power to DC

Explanation

The end-of-line resistor establishes a supervised reference so the panel can detect open or shorted wiring on the circuit. Its placement at the far end of the loop is essential for complete supervision.

Question 9Fire Alarm Systems and Code Requirements

A technician finds that a notification appliance circuit serving horns and strobes does not operate during an alarm but the panel shows no trouble. What is the most appropriate first step?

  1. Replace the main control panel
  2. Verify that the NAC output is programmed and enabled for the alarm event Correct answer.
  3. Increase the battery capacity
  4. Disconnect the end-of-line resistor

Explanation

If the panel reports no trouble, the circuit is likely intact but the output may not be mapped or enabled for the alarm event. Confirming programming before replacing hardware is the correct diagnostic sequence.

Question 10Fire Alarm Systems and Code Requirements

In a fully sprinklered building, when are smoke detectors generally required in addition to the sprinkler protection for a fire alarm system?

  1. Never, because sprinklers provide complete coverage
  2. Only when required by the building code or a specific detection objective, such as early warning or smoke control Correct answer.
  3. Only when the building exceeds ten stories
  4. Only in elevator machine rooms

Explanation

Sprinklers do not eliminate all detection requirements; the building code or a specific design objective may require smoke detection. The need is determined by occupancy, egress, and smoke control provisions.

Question 11Fire Alarm Systems and Code Requirements

A spot-type smoke detector is being placed on a ceiling with a beam depth of 18 inches and beam spacing of 10 feet. How should placement be handled?

  1. Space detectors at the listed smooth-ceiling spacing without adjustment
  2. Ignore the beams and treat the ceiling as smooth
  3. Place detectors on the ceiling within each beam pocket as required for the ceiling configuration Correct answer.
  4. Mount detectors on the beam bottoms only

Explanation

Beams can create pockets that affect smoke accumulation, so detectors are placed within each pocket according to the ceiling configuration rules. Smooth-ceiling spacing cannot simply be applied across deep beams.

Question 12Fire Alarm Systems and Code Requirements

What is the significance of a listed compatible device when adding components to an existing addressable fire alarm system?

  1. It allows the device to bypass the panel's programming
  2. It guarantees the device will last the life of the building
  3. It permits the device to be installed without any wiring supervision
  4. It ensures the device has been evaluated for interoperability with the system Correct answer.

Explanation

Listed compatibility confirms that the device has been evaluated to work with the specific system, protecting performance and listing integrity. Non-compatible devices can cause communication faults or unreliable operation.

Question 13Fire Alarm Systems and Code Requirements

During acceptance testing, how should the alarm signal be verified for audibility in a sleeping area?

  1. By listening at the panel location
  2. By confirming the panel displays an alarm
  3. By measuring sound pressure level in the room with the door closed and comparing it to the code-required threshold Correct answer.
  4. By checking the strobe flash rate

Explanation

Audibility in sleeping areas is verified by measuring sound pressure at the pillow or within the room under the conditions specified by code. Panel indication alone does not confirm adequate notification.

Question 14Fire Alarm Systems and Code Requirements

A waterflow switch on a sprinkler system is connected to the fire alarm panel. Which signal should it initiate when water flows?

  1. An alarm signal Correct answer.
  2. A trouble signal
  3. A security signal
  4. A supervisory signal

Explanation

A waterflow switch indicates that water is discharging, which is an alarm condition. Supervisory signals are reserved for off-normal conditions such as closed valves.

Question 15Fire Alarm Systems and Code Requirements

Why does NFPA 72 require that fire alarm cables be separated from other electrical circuits or protected by a listed barrier?

  1. To reduce the cost of installation
  2. To prevent electromagnetic interference and physical damage that could impair system reliability Correct answer.
  3. To eliminate the need for grounding
  4. To simplify the panel's programming

Explanation

Separation protects fire alarm circuits from interference and damage that could cause false alarms or failures. Grounding and other requirements still apply independently.

Question 16Fire Alarm Systems and Code Requirements

A building owner wants to use a temporary disconnect to silence a nuisance alarm at 2 a.m. What is the appropriate action?

  1. Disable the device at the panel and leave it disabled until the next inspection
  2. Remove the detector from its base
  3. Shut off the panel's primary power
  4. Silence the notification appliances using the panel's alarm silence function and investigate the cause Correct answer.

Explanation

Alarm silence is a designed function that stops the notification appliances while maintaining system integrity. Disabling devices or removing power compromises protection and must be avoided.

Question 17Fire Alarm Systems and Code Requirements

What does the term 'positive alarm sequence' describe in a fire alarm system?

  1. A sequence that requires two detectors to alarm simultaneously
  2. A programming feature that silences all alarms automatically
  3. A feature that delays notification for a set period to allow investigation, with automatic alarm if not acknowledged Correct answer.
  4. A method of testing batteries in sequence

Explanation

Positive alarm sequence permits a brief investigation period after an alarm before general notification, but escalates automatically if the alarm is not acknowledged. This reduces disruption from nuisance alarms while preserving response.

Question 18Fire Alarm Systems and Code Requirements

In an addressable system, what is the primary benefit of device-level addressing compared with conventional zoning?

  1. It eliminates the need for an end-of-line resistor on all circuits
  2. It removes the requirement for periodic testing
  3. It reduces the number of wires needed for the notification appliances
  4. It allows the control unit to identify the specific device that initiated an alarm or trouble Correct answer.

Explanation

Addressable systems report the individual device identity, which speeds response and troubleshooting. Testing and supervision requirements still apply to the system as a whole.

Question 19Fire Alarm Systems and Code Requirements

A designer is placing visible notification appliances in a corridor. Which factor most directly determines the required spacing and intensity?

  1. The color of the corridor walls
  2. The mounting height and the corridor width, evaluated against the code's coverage criteria Correct answer.
  3. The age of the building
  4. The number of occupants assigned to the floor

Explanation

Visible appliance coverage depends on mounting height, room or corridor dimensions, and the applicable candela rating. Wall color and occupant counts do not establish spacing under the code.

Question 20Fire Alarm Systems and Code Requirements

What is the purpose of a ground fault detection circuit in a fire alarm control unit?

  1. To verify the sound output of horns
  2. To measure the resistance of the notification appliances
  3. To test the battery electrolyte level
  4. To identify an unintended connection between a system conductor and ground that could impair operation Correct answer.

Explanation

Ground fault detection identifies unintended ground connections that can cause circuit malfunction or false operation. It is a supervision function distinct from device testing.

Question 21Fire Alarm Systems and Code Requirements

An engineer is evaluating whether a high-rise building needs a voice evacuation system instead of a horn-based system. Which consideration most strongly supports voice evacuation?

  1. The building has a small occupant load
  2. The building uses conventional initiating circuits
  3. The building requires phased evacuation or specific occupant instructions during an emergency Correct answer.
  4. The building has a single exit

Explanation

Voice systems support phased evacuation and live or prerecorded instructions that horns cannot provide. Small occupant loads or single exits do not by themselves justify voice capability.

Question 22Fire Alarm Systems and Code Requirements

During a sensitivity test of a spot-type smoke detector, the measured value falls outside the listed sensitivity range. What is the correct action?

  1. Ignore the result if the detector alarmed during the test
  2. Increase the panel's alarm threshold globally
  3. Adjust the detector or replace it, then retest to confirm it is within the listed range Correct answer.
  4. Reduce the detector spacing in the design drawings

Explanation

Detectors found outside their listed sensitivity range must be adjusted or replaced and retested. Global threshold changes or ignoring the result would leave the system noncompliant.

Question 23Fire Alarm Systems and Code Requirements

A smoke control system uses smoke detectors to trigger stairwell pressurization. Which coordination issue is most critical for reliable operation?

  1. The detectors must be on the same NAC as the horns
  2. The detectors must use the same brand as the notification appliances
  3. The detection signal must reliably initiate the smoke control sequence and be monitored for integrity Correct answer.
  4. The detectors must be the lowest-address devices on the loop

Explanation

Smoke control relies on a dependable detection signal and monitored integrity of the initiating and control circuits. Device addressing order or brand matching does not determine reliability.

Question 24Fire Alarm Systems and Code Requirements

A technician is troubleshooting intermittent false alarms from a photoelectric detector located near a supply diffuser. What is the most likely cause?

  1. The detector is beyond its listed sensitivity range because of airflow and airborne particles Correct answer.
  2. The notification appliances are drawing too much current
  3. The battery is fully charged
  4. The end-of-line resistor is missing

Explanation

Airflow from a diffuser can carry particles or cause pressure effects that produce intermittent alarms. Relocating or re-evaluating the detector placement is the appropriate corrective action.

Question 25Fire Alarm Systems and Code Requirements

When evaluating whether a detector's placement complies with NFPA 72 near a wall, what general rule applies to spot-type smoke detectors on a smooth ceiling?

  1. Detectors should be located at least the listed distance from the wall, typically based on the detector's spacing Correct answer.
  2. Detectors may be placed flush against the wall
  3. Detectors must be mounted on the wall, not the ceiling
  4. Detectors must be centered in the room only

Explanation

Spot-type detectors are kept a minimum distance from walls and partitions because dead air spaces reduce response. The distance is derived from the listed spacing, commonly one-half the spacing value in many applications.

Question 26Fire Alarm Systems and Code Requirements

Under NFPA 72, which signal type must a fire alarm control unit be capable of transmitting to a supervising station to indicate a problem with the system's wiring or circuitry that could impair its operation?

  1. Trouble signal Correct answer.
  2. Supervisory signal
  3. Evacuation signal
  4. Alarm signal

Explanation

NFPA 72 defines four signal categories: alarm, supervisory, trouble, and (for some systems) emergency/evacuation. A trouble signal specifically indicates a fault in the system itself, such as an open circuit, ground fault, or loss of primary power, that may compromise reliability. Supervisory signals are reserved for off-normal conditions of suppression systems, not for panel circuitry faults.

Question 27Fire Alarm Systems and Code Requirements

A designer is selecting a heat detector for a kitchen hood area where normal cooking operations produce rapid temperature rises. Which detector characteristic is most important to avoid nuisance actuation?

  1. Fixed-temperature setpoint only
  2. Detector spacing reduction
  3. Rate-of-rise sensitivity threshold Correct answer.
  4. Higher voltage rating

Explanation

Rate-of-rise heat detectors respond to the speed of temperature increase and can be triggered by normal cooking cycles, so the rate threshold must be evaluated carefully. Fixed-temperature devices are less affected by short transient rises but still need an appropriate setpoint. Spacing and voltage do not address nuisance response to rapid temperature changes.

Question 28Fire Alarm Systems and Code Requirements

What is the primary purpose of a fire alarm system's annunciator panel in a large building?

  1. To provide backup power to initiating devices during an outage
  2. To amplify the audible output of notification appliances
  3. To display the location and status of alarm, supervisory, and trouble conditions remotely from the main panel Correct answer.
  4. To perform sensitivity testing of smoke detectors automatically

Explanation

An annunciator provides a remote display, typically at an entrance or staffed location, showing the zone or device in alarm and any supervisory or trouble conditions. It does not generate power, test detectors, or amplify sound; those functions belong to the control unit, power supply, or notification circuits.

Question 29Fire Alarm Systems and Code Requirements

A technician must verify that an initiating device circuit is properly supervised. Which condition should the control unit report if the circuit wiring is opened?

  1. A trouble condition Correct answer.
  2. A supervisory condition
  3. A waterflow alarm
  4. A pre-signal alarm

Explanation

Initiating device circuits are supervised so that an open, short, or ground fault produces a trouble signal, alerting building staff that detection may be impaired. This supervision is separate from the alarm signal produced by an actual device activation. Supervisory signals apply to suppression system conditions, and pre-signal is an alarm processing feature.

Question 30Fire Alarm Systems and Code Requirements

Which of the following best describes the function of a manual fire alarm pull station?

  1. To silence notification appliances at the panel
  2. To automatically detect smoke and initiate an alarm
  3. To allow a person to initiate an alarm signal by manual means Correct answer.
  4. To reset the control unit after an alarm

Explanation

A manual pull station is a manually operated initiating device that lets an occupant trigger the alarm system without waiting for automatic detection. Automatic detection is the role of smoke or heat detectors, while silencing and resetting are control unit functions. Pull stations are typically located along exit paths for accessibility.

Question 31Fire Alarm Systems and Code Requirements

During a design review, an engineer notes that a corridor is 8 feet wide and 60 feet long. Which general NFPA 72 consideration most directly affects visible appliance placement in this corridor?

  1. Visible appliances must be installed only at the corridor midpoint
  2. Visible appliances must be spaced so that the entire corridor length is within the rated viewing distance, often with appliances at each end Correct answer.
  3. Visible appliances must be omitted if audible appliances are present
  4. Visible appliances must be mounted at the ceiling regardless of corridor length

Explanation

For corridors, NFPA 72 generally requires visible appliances to be arranged so that the required illumination is maintained throughout, commonly by placing appliances at each end or spacing them based on the listed viewing distance. A single midpoint device may leave the ends inadequately covered. Ceiling-only mounting and omission in favor of audible devices are not correct general rules.

Question 32Fire Alarm Systems and Code Requirements

What is the purpose of a smoke detector's listed sensitivity range?

  1. To define the obscuration levels at which the detector is expected to respond and remain within its listed performance Correct answer.
  2. To determine the audible output of the detector's sounder
  3. To specify the maximum voltage the detector can accept
  4. To set the maximum spacing between detectors

Explanation

The listed sensitivity range defines the smoke obscuration levels at which the detector should alarm, and periodic testing verifies the device remains within that range. Voltage, spacing, and sound output are separate design and listing parameters. A detector drifting outside its listed range may fail to respond or cause nuisance alarms.

Question 33Fire Alarm Systems and Code Requirements

An addressable fire alarm system uses a signaling line circuit (SLC). Which statement best describes the SLC's role?

  1. It supplies branch circuit power to notification appliances only
  2. It provides the primary 120-volt AC feed to the building
  3. It carries data between the control unit and addressable devices while also providing power to those devices Correct answer.
  4. It connects the panel to the municipal water supply

Explanation

The signaling line circuit is the data pathway that lets the control unit communicate individually with addressable initiating and other devices, and it typically also carries operating power to them. Notification appliance circuits are separate, and the SLC has no role in water supply or building AC distribution.

Question 34Fire Alarm Systems and Code Requirements

A fire alarm system is being installed in a building with a standby generator. What is the primary reason NFPA 72 requires the fire alarm control unit to be connected to a dedicated branch circuit?

  1. To allow the panel to control the generator
  2. To help ensure the system is not inadvertently disconnected by other equipment on the same circuit Correct answer.
  3. To increase the voltage available to notification appliances
  4. To eliminate the need for battery backup

Explanation

A dedicated branch circuit reduces the chance that unrelated equipment or a switched circuit will remove power from the fire alarm control unit. It does not boost appliance voltage, control the generator, or remove the requirement for standby batteries. Battery backup remains necessary for primary power loss.

Question 35Fire Alarm Systems and Code Requirements

Which of the following is the correct action when a smoke detector is found to be excessively dirty during inspection?

  1. Reduce the detector's coverage area by adding a second device
  2. Clean or replace the detector according to the manufacturer's instructions and retest it Correct answer.
  3. Increase the detector's sensitivity setting to compensate
  4. Disconnect the detector until the next scheduled inspection

Explanation

Dirty detectors can drift out of their listed sensitivity range or cause nuisance alarms, so the manufacturer's cleaning or replacement procedure should be followed and the device retested. Adjusting sensitivity, leaving the device disconnected, or adding devices does not correct the underlying condition and may violate code or listing.

Question 36Fire Alarm Systems and Code Requirements

A building has a fire alarm system with a voice evacuation capability. What distinguishes a voice evacuation system from a simple horn-based notification system?

  1. It eliminates the need for manual pull stations
  2. It requires no standby power source
  3. It uses only visible appliances for notification
  4. It can deliver intelligible voice messages to guide occupants during an emergency Correct answer.

Explanation

Voice evacuation systems use amplified audio to broadcast intelligible spoken instructions, which can convey more specific direction than a generic horn signal. They still require visible notification where applicable, manual initiation, and standby power. The distinguishing feature is the voice message capability.

Question 37Fire Alarm Systems and Code Requirements

A technician is testing a notification appliance circuit and finds that the voltage at the last appliance is significantly lower than at the first. Which condition most likely explains this?

  1. A misaddressed smoke detector
  2. Voltage drop along the circuit due to conductor resistance Correct answer.
  3. An open supervisory switch
  4. A ground fault on the initiating circuit

Explanation

Conductor resistance causes voltage to drop progressively along a notification appliance circuit, which can leave distant appliances underpowered. Designers must account for this by sizing conductors and limiting circuit loading. Ground faults, supervisory switches, and detector addressing affect other parts of the system.

Question 38Fire Alarm Systems and Code Requirements

In a system using alarm verification, what is the effect of the verification feature on signal processing?

  1. It converts a supervisory signal into a trouble signal
  2. It immediately transmits the alarm without any delay
  3. It delays alarm processing briefly to allow a detector to reset, reducing nuisance alarms from transient conditions Correct answer.
  4. It bypasses the control unit and sends the alarm directly to the fire department

Explanation

Alarm verification introduces a short delay and reset period so that a transient condition, such as dust or steam, does not immediately produce a full alarm. If the detector remains in alarm after the verification period, the alarm is processed. It does not transmit instantly, convert signal types, or bypass the control unit.

Question 39Fire Alarm Systems and Code Requirements

Which factor most directly determines whether a fire alarm system must be monitored by a supervising station in a given occupancy?

  1. The applicable code and the occupancy's requirements for remote notification Correct answer.
  2. The brand of the control unit
  3. The color of the notification appliances
  4. The number of manual pull stations installed

Explanation

Remote supervision requirements come from the applicable building or fire code and the occupancy classification, which may require central station, proprietary, or remote station monitoring. Device counts, appliance color, and panel brand do not determine monitoring requirements. The authority having jurisdiction also plays a role in enforcement.

Question 40Fire Alarm Systems and Code Requirements

A fire alarm system's batteries must be sized to support the system during a primary power outage. Which load condition is typically used for this calculation?

  1. Standby load for the required duration plus alarm load for a specified period Correct answer.
  2. Standby load only, with no alarm period
  3. Alarm load only, with no standby period
  4. Peak notification load for the entire standby duration

Explanation

Battery sizing generally combines the standby current for the required duration with the alarm current for a specified period, reflecting the need to operate through an outage and then sound an alarm. Using only one load condition or assuming peak alarm load throughout standby overstates or understates the requirement incorrectly. Manufacturer instructions and code define the exact durations.

Question 41Electrical Theory and Power Supplies

A fire alarm control panel is powered from a 120 V AC branch circuit through a step-down transformer. Which relationship correctly describes the transformer's voltage and current behavior under ideal conditions?

  1. Voltage steps down while current capability steps up in inverse proportion Correct answer.
  2. Voltage and current both remain unchanged regardless of turns ratio
  3. Voltage steps down while power output increases beyond the input
  4. Voltage steps down and current capability steps down in the same proportion

Explanation

An ideal transformer conserves power, so the product of voltage and current is the same on both windings. When the secondary voltage is lower, the secondary current capability rises by the same turns ratio. This is why a 120 V to 24 V transformer can supply relatively high current on the secondary from a modest primary current.

Question 42Electrical Theory and Power Supplies

A notification appliance circuit is rated 24 V DC and draws 2.5 A while sounding. What power does the circuit consume?

  1. 0.104 W
  2. 26.5 W
  3. 60 W Correct answer.
  4. 9.6 W

Explanation

DC power equals voltage multiplied by current, so 24 V times 2.5 A gives 60 W. This value matters when totaling appliance load against the panel's power supply capacity. Multiplying incorrectly or dividing the values produces the other answers.

Question 43Electrical Theory and Power Supplies

Which conductor property most directly determines its resistance for a fixed length at a constant temperature?

  1. Cross-sectional area Correct answer.
  2. Insulation color
  3. Jacket thickness
  4. Strand count

Explanation

Resistance of a conductor is inversely proportional to its cross-sectional area for a given length and material. A larger area provides more paths for electron flow, lowering resistance and voltage drop. Color, stranding style, and jacket thickness do not change the resistance of the metal itself.

Question 44Electrical Theory and Power Supplies

Two 10 kΩ resistors are connected in parallel across a 24 V source. What is the total current drawn from the source?

  1. 2.4 mA
  2. 0.48 mA
  3. 4.8 mA Correct answer.
  4. 1.2 mA

Explanation

Two equal resistors in parallel have an equivalent resistance of half the value, so 5 kΩ. Using Ohm's law, 24 V divided by 5 kΩ equals 4.8 mA. Each branch carries 2.4 mA and the branches sum to the total.

Question 45Electrical Theory and Power Supplies

A 24 V DC notification circuit runs 250 ft of two-conductor cable to a horn drawing 1 A. If the total loop resistance of the cable is 2.5 Ω, what approximate voltage reaches the horn?

  1. 21.5 V Correct answer.
  2. 26.5 V
  3. 24 V
  4. 2.5 V

Explanation

The cable drop equals current times loop resistance, or 1 A times 2.5 Ω, giving 2.5 V lost in the conductors. Subtracting that from the 24 V source leaves about 21.5 V at the appliance. Excessive drop can cause appliances to operate outside their listed voltage range.

Question 46Electrical Theory and Power Supplies

A sealed lead-acid battery bank for a fire panel is rated 24 V and 18 Ah. Which statement best describes the meaning of the amp-hour rating?

  1. It can deliver about 18 A for one hour before reaching its end voltage Correct answer.
  2. It holds 18 V of charge per cell
  3. It delivers 18 W of power for one hour
  4. It can deliver exactly 18 A indefinitely without recharging

Explanation

Amp-hour capacity expresses the product of discharge current and time for a defined discharge rate to a specified end voltage. An 18 Ah rating approximates 18 A for one hour or 1.8 A for ten hours, though higher rates reduce usable capacity. It is a charge quantity, not a power or voltage figure.

Question 47Electrical Theory and Power Supplies

Which condition is required for a fire alarm control panel's standby battery calculation to be considered adequate?

  1. Batteries must match the panel's maximum charging current in amp-hours
  2. Batteries must carry the alarm load only for five minutes
  3. Batteries must supply the panel's normal AC load indefinitely
  4. Batteries must carry standby load for the required time plus alarm load for the required time Correct answer.

Explanation

Standby calculations add the supervisory current over the code-specified standby period to the alarm current over the alarm period, with a derating factor for aging and efficiency. This ensures the system remains functional through an outage and a subsequent alarm. Alarm-only or AC-only figures do not satisfy the requirement.

Question 48Electrical Theory and Power Supplies

In a DC circuit, which device is used to limit current to a notification appliance to protect it from overcurrent?

  1. A capacitor placed across the supply
  2. An inductor placed in parallel with the load
  3. A series resistor sized for the appliance Correct answer.
  4. A diode placed in parallel with the load

Explanation

A resistor in series with the load drops voltage and limits current according to Ohm's law. Sizing the resistor for the appliance's rated current protects it from overcurrent. Reactive components placed in parallel do not provide steady current limiting.

Question 49Electrical Theory and Power Supplies

A fire alarm system uses a 24 V DC supply with a 2 A current limit. Four horns each draw 0.4 A and are wired in parallel. What happens when all four sound simultaneously?

  1. Total draw is 0.1 A, well within the limit
  2. Total draw is 1.6 A, within the supply limit Correct answer.
  3. Total draw is 0.4 A because parallel loads share current
  4. Total draw is 3.2 A, exceeding the supply limit

Explanation

Parallel loads each receive the full supply voltage and their currents add. Four horns at 0.4 A each total 1.6 A, which is below the 2 A limit. If the total exceeded the limit, the supply would current-limit or trip.

Question 50Electrical Theory and Power Supplies

Which wiring fault most commonly causes a ground fault indication on a fire alarm circuit?

  1. An unintended connection between a circuit conductor and earth ground Correct answer.
  2. A loose terminal on a notification appliance
  3. A reversed polarity at a smoke detector base
  4. An open resistor in a current-limiting module

Explanation

A ground fault occurs when a conductor unintentionally contacts ground, allowing current to flow through an unintended path. The panel detects this imbalance or leakage and annunciates a trouble condition. Loose terminals, polarity errors, and component failures produce different trouble types.