Arizona Low Voltage Practice flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ohm's Law

The relationship among voltage, current, and resistance in a circuit: E equals I multiplied by R. Rearranged, current equals voltage divided by resistance, and resistance equals voltage divided by current.

Power Formula

Electrical power in watts equals voltage multiplied by current. Substituting Ohm's Law gives P equals I squared times R, or P equals E squared divided by R.

Series Circuit Rules

In a series circuit the same current flows through every component, total resistance is the sum of individual resistances, and the voltage divides across components in proportion to their resistance.

Parallel Circuit Rules

In a parallel circuit the voltage is the same across every branch, branch currents add to give total current, and total resistance is found from the reciprocal sum of the branch resistances.

Voltage Drop Formula

For a two-wire circuit, voltage drop equals two times the resistivity constant K, times current, times one-way length in feet, divided by conductor area in circular mils.

Circular Mil Definition

A circular mil is the area of a circle one thousandth of an inch in diameter. Conductor area in circular mils equals the diameter in mils squared.

Class 2 Circuit Limits

Class 2 circuits are power-limited by a listed transformer or supply. NEC Chapter 9 Tables 11(A) and 11(B) set the maximum voltage and current for the circuit.

NEC Article 725 Scope

Article 725 governs Class 1, Class 2, and Class 3 remote-control, signaling, and power-limited circuits that are not part of a communications or fire alarm system.

Plenum Cable Rating CMP

CMP cable is listed for installation in ducts and plenum spaces used for environmental air. It has the lowest flame spread and smoke production of the copper cable ratings.

Cable Substitution Rule

A cable with a higher fire-resistance or circuit-integrity rating may replace a lower-rated cable in the same location, but a lower-rated cable may never replace a higher-rated one.

Power and Signal Separation

Class 2 and Class 3 cables must be kept at least two inches from electric light and power conductors unless a raceway, cable sheath, or permanent barrier provides separation.

Twisted Pair Bend Radius

Four-pair balanced twisted-pair cable must not be bent tighter than four times its diameter during installation, or eight times its diameter after installation is complete.

Firestop Penetration Requirement

Openings made through fire-rated walls or floors for cables must be sealed with a listed firestop system approved for that specific cable type and penetration arrangement.

Bonding Versus Grounding

Bonding intentionally connects metallic parts to form a conductive path that carries fault current. Grounding connects the system to earth. Bonding clears faults; grounding alone does not.

Telecom Bonding Conductor Size

NEC Table 800.100(A) sizes the telecommunications bonding conductor by length: 14 AWG copper up to 6 feet, 12 AWG up to 10 feet, and 6 AWG up to 18 feet.

Primary Protector Requirement

A listed primary protector is required where communications conductors enter a building, and it must be bonded to the building grounding electrode system near the entry point.

GFCI Protection Locations

Ground-fault circuit interrupter protection is required in bathrooms, kitchens, garages, outdoors, wet locations, and within six feet of sinks, per NEC Article 210.8.

Equipment Grounding Conductor

The equipment grounding conductor provides a low-impedance fault path back to the source. It must be continuous, connected to every enclosure, and sized per NEC Table 250.122.

NFPA 72 Scope

NFPA 72 is the National Fire Alarm and Signaling Code. It sets requirements for the installation, inspection, testing, and maintenance of fire detection and notification systems.

Smoke Detector Spacing

On a smooth ceiling, smoke detectors are spaced no more than 30 feet apart, with the first detector within 15 feet of any wall and at least 4 inches from it.

Heat Detector Spacing

Listed fixed-temperature heat detectors rated 135 to 174 degrees Fahrenheit are spaced up to 50 feet apart on smooth ceilings, reduced for high ceilings per NFPA 72 factors.

Notification Appliance Circuit

A notification appliance circuit supplies and supervises horns, strobes, and speakers. Voltage drop must be calculated so the last appliance receives its listed minimum operating voltage.

Survivable Fire Alarm Cable

Circuit integrity cable, marked CI, is listed to remain operational during a fire for a specified time and must be installed according to its listing conditions.

Fail-Safe Versus Fail-Secure

Fail-safe locks release when power is lost and are used on egress doors. Fail-secure locks stay locked when power is lost and are used where security outweighs egress concerns.

Wiegand Interface

Wiegand is a legacy access control signaling interface that sends credential data as pulses on data-zero and data-one lines, commonly in 26-bit to 40-bit formats.

Power over Ethernet Standards

IEEE 802.3af supplies up to 15.4 watts at the source, 802.3at up to 30 watts, and 802.3bt up to 60 or 90 watts, with lower power available at the device.

Video Storage Calculation

Storage in bytes approximately equals bit rate in bits per second times 3600 seconds per hour times recording hours, divided by eight, summed over all cameras and retention days.

T568A and T568B Pinouts

These are the two standard pin assignments for eight-position modular jacks. Either is acceptable, but the same standard must be used throughout a given cabling project.

Horizontal Cabling Distance

The permanent horizontal link is limited to 90 meters, or 295 feet. Adding patch cords at each end gives a maximum channel length of 100 meters, or 328 feet.

Category Cable Frequencies

Category 5e cable is rated to 100 MHz, Category 6 to 250 MHz, Category 6A to 500 MHz, and Category 8 to 2000 MHz over a limited 30-meter distance.

Constant Voltage Audio Line

A 70.7-volt or 100-volt distributed audio system places many speakers on one line. The sum of all speaker wattage taps must not exceed the amplifier's rated output.

Arizona ROC License Number

Arizona contractors must display their Registrar of Contractors license number on advertising, bids, and contracts. Unlicensed contracting is a criminal offense under state law.