Free TN LLE Exam Flashcards

A complete circuit provides an unbroken path from the source through the load and back to the source. An open circuit interrupts that path, so normal load current cannot flow even though voltage may still be present at part of the circuit.

Parallel loads each receive the circuit voltage and can operate independently. In a series arrangement, the voltage divides among loads and one open load can interrupt current through the whole path.

Use V = I × R. Rearrange it as I = V ÷ R or R = V ÷ I, then keep units consistent and check whether the result is reasonable for the circuit described.

Start with P = V × I. By combining it with Ohm's law, you can also use P = I²R or P = V² ÷ R when the known quantities make either form faster.

The NEC treats a load expected to run at maximum current for three hours or more as continuous. Applicable conductor and overcurrent-device calculations generally include 125% of that continuous portion, so classification comes before sizing.

The installation must follow the conditions under which the product was evaluated and marked. A field shortcut that conflicts with the listing or label can make an otherwise familiar product noncompliant.

It gives qualified people safe access to inspect, adjust, service, or maintain equipment that may be energized. The space is not intended for storage, and its required dimensions depend on the equipment and conditions.

Close them with an identified method that restores protection substantially equivalent to the enclosure wall. An open knockout can expose live parts and admit debris or moisture.

Clear, durable identification lets a worker isolate the correct circuit or equipment without trial and error. Labels should describe the actual purpose or area served rather than rely on vague wording.

Service conductors bring power from the service point to the service disconnect. Feeders run from service or other source equipment to downstream distribution, while branch-circuit conductors run from the final overcurrent device to outlets or loads.

It marks the boundary where the serving utility's conductors connect to the premises wiring. Identifying that boundary helps determine which conductors and equipment fall under the NEC service provisions.

Service equipment provides the principal control and cutoff for the building or structure’s supply. Required service overcurrent protection must be integral to the service disconnecting means or located immediately adjacent to it, and the equipment must be suitable for use as service equipment.

Inventory the connected loads, classify them, apply only the demand factors and allowances that fit those load types, add continuous-load treatment where required, and then size conductors and protection from the resulting load.

The rating is generally set by the overcurrent device protecting the circuit. Conductor ampacity, outlet rules, and the permitted load must all be checked against that rating rather than considered in isolation.

Simultaneous disconnection prevents someone from treating a shared-neutral circuit as de-energized while another ungrounded conductor remains live. It is a personnel-safety control, not merely a convenience.

GFCI protection reacts to current imbalance that can indicate leakage and shock risk. AFCI protection detects signatures associated with dangerous arcing that can ignite materials. A location may require one or both.

First identify whether the outlet serves the kitchen, pantry, breakfast, dining, or similar area, then check the required number and rating of small-appliance circuits and the restrictions on other outlets they may serve.

For opposing legs of a single-phase system, the neutral carries the imbalance between the ungrounded-conductor currents rather than their arithmetic sum. Nonlinear loads and other system arrangements require separate analysis.

An overload is excessive current in an otherwise normal current path. A short circuit or ground fault creates an unintended low-impedance path and can produce much higher fault current, demanding rapid interruption.

The device must protect the conductors while also accommodating the permitted load and any equipment-specific rule. Choosing the breaker or fuse first can hide an undersized conductor or an impermissible load.

It is an exception available only when all stated conditions are met, including limits on device size, conductor ampacity, circuit type, and equipment rules. If a specific article requires another size, that specific rule controls.

Grounding connects a system or equipment to earth. Bonding joins conductive parts to establish electrical continuity and an effective fault-current path. Earth alone is not the normal path relied on to clear a fault.

The grounded conductor, often the neutral, normally carries return current. The equipment grounding conductor normally carries current only during faults and bonds non-current-carrying metal parts back to the source.

It must be intentionally constructed, electrically continuous, and low enough in impedance to carry fault current back to the source so the protective device opens promptly.

The grounding electrode conductor connects the grounded system or equipment to the grounding electrode system. The equipment grounding conductor links equipment enclosures and other metal parts into the fault-current return path.

An extra connection can place normal neutral current on equipment grounding paths and metal parts, creating objectionable current. Downstream neutrals and equipment grounding conductors are normally kept isolated unless a specific rule says otherwise.

Ask whether the new source has a direct electrical connection, including a solidly connected grounded conductor, to conductors from another system. If it does not, separately derived system grounding and bonding rules may apply.

Identify conductor material, insulation rating, ambient temperature, number of current-carrying conductors, terminal temperature limits, load type, and any equipment-specific rule before selecting and adjusting an ampacity.

Equipment terminals may have a lower temperature rating than the conductor insulation. The final ampacity must respect the terminal limitation, though a higher insulation rating may still be used for correction or adjustment calculations where permitted.

Temperature correction accounts for an environment hotter or colder than the table basis. Adjustment accounts for heat from multiple current-carrying conductors grouped together. Both can apply to the same installation.

The inside of a raceway in a wet location is treated as wet because moisture and condensation can enter. A dry-location-only insulation marking is not made acceptable merely by enclosing the conductor.

White or gray normally identifies a grounded conductor, while green or bare identifies equipment grounding. Limited reidentification rules exist, so verify the conductor type, wiring method, size, and permitted use before remarking it.

Use the raceway's usable internal area, the area of each conductor, and the applicable percentage for the number and type of conductors. Do not confuse fill calculations with ampacity adjustment.

Count insulated conductors, internal clamps, support fittings, devices, and equipment grounding conductors under their respective rules, then multiply each allowance by the volume assigned to the conductor size involved.

Under the 2017 NEC method, all equipment grounding conductors in the box together receive one conductor-volume allowance, based on the largest equipment grounding conductor present. Do not count each one like an insulated current-carrying conductor.

They provide accessible points for pulling, changing direction, or making permitted splices without subjecting conductors to damaging bends or excessive pulling force. Their dimensions depend on conductor size and pull geometry.

They must suit the environment where installed, such as wet, damp, corrosive, or hazardous conditions. The enclosure and fittings work as a system, so one unsuitable component can defeat the intended protection.

Bends must not damage the raceway or reduce its internal diameter improperly, and the completed run must be securely fastened and supported at the intervals and locations required for that raceway type.

Identify the hazardous material, how it may be present, and the classified extent of the location. Equipment selection follows the classification; it should not be guessed from the building's general use.

Class I involves flammable gases or vapors that may create an ignitable mixture. The division or zone and the material group further control acceptable wiring methods and equipment.

Class II involves combustible dust. Dust characteristics, whether hazardous concentrations are normally present, and the chance of dust accumulation affect the detailed classification.

Class III involves easily ignitable fibers or flyings that are handled, manufactured, or used but are not normally suspended in the air in quantities likely to create an ignitable mixture.

Division 1 describes conditions where the hazard can exist during normal operation or frequently. Division 2 generally describes a hazard that is normally confined and appears mainly through abnormal failure or breakdown.

A properly installed seal limits the passage of gases, vapors, or flames through the raceway and helps contain an explosion within approved equipment. Its location and installation must follow the applicable classification rules.

Required separation or an approved barrier prevents higher voltage from being introduced into a circuit whose wiring and connected equipment rely on power limitation. Apply the rule for the circuit class and enclosure involved.

Identify the system first—such as fire alarm, Class 2 or Class 3 remote-control, optical fiber, or communications—then go to its governing article before applying separation, support, grounding, or listing rules.

Confirm the luminaire is identified for the actual environment and that water cannot enter or accumulate in wiring compartments or live parts. A damp-location rating is not interchangeable with a wet-location rating.

Cords are vulnerable to physical damage and are intended only for permitted flexible connections. They generally cannot be concealed through building surfaces or used to bypass the permanent wiring method required for the installation.

It allows the sign and associated controller to be isolated for service or emergency response. The disconnect must be accessible, properly located for the installation, and capable of disconnecting the required conductors.

Use the appliance nameplate together with its applicable NEC article: identify the load, continuous-duty treatment if any, conductor rule, overcurrent protection, disconnect, and whether an individual branch circuit is required.