MTTC Electrical Trade Test key terms

A formal safety procedure that isolates energy sources, applies a personal lock and tag, and verifies de-energization before work begins on equipment. It prevents accidental re-energization or release of stored energy.

The approach distance at which an exposed person could receive a second-degree burn from an arc flash. It is calculated from incident energy and defines where arc-rated protection is required.

Wearing apparel and gear, such as arc-rated clothing, gloves, and face shields, selected to protect a worker from electrical, thermal, and physical hazards for the task and voltage involved.

Acceptable to the authority having jurisdiction. In code language, the term means an inspector has judged the equipment or material suitable for its intended use, not merely that it is listed.

The organization, office, or individual responsible for enforcing code requirements and approving equipment, materials, and installations. Local building or electrical inspectors typically serve as the AHJ.

The clear, accessible space required in front of electrical equipment so a person can safely work on it. Depth depends on voltage and whether live parts are exposed on one or both sides.

The relationship stating that voltage equals current multiplied by resistance (E = I × R). It allows any one electrical quantity to be calculated when the other two are known in a circuit.

The relationship describing electrical power in watts as voltage times current (P = E × I), with power-factor correction applied in alternating-current circuits. It is used to size conductors and equipment.

The ratio of true power in watts to apparent power in volt-amperes in an alternating-current circuit. A low power factor means more current is needed to deliver the same useful work.

The total opposition to alternating current flow, combining resistance and reactance. It is measured in ohms and determines current when alternating voltage is applied to a circuit.

The property of a coil that opposes a change in current by producing a counter-electromotive force. It causes current to lag voltage and is measured in henries.

The ability of two separated conductors to store electric charge, measured in farads. In alternating-current circuits, capacitive reactance causes current to lead voltage.

Two basic connection arrangements. In series, current is common and voltage divides; in parallel, voltage is common and current divides. Recognizing each helps predict resistance and load behavior.

An alternating-current supply using three conductors whose voltages are offset by 120 electrical degrees. It delivers constant power and is common for motors and large distribution systems.

Two ways to connect three-phase windings or loads. Wye joins one end of each winding at a neutral point; delta connects them in a closed loop, changing voltage and current relationships.

A device that transfers energy between circuits by electromagnetic induction, raising or lowering alternating voltage while keeping frequency constant. It operates on alternating current only.

The maximum current a conductor can carry continuously under stated conditions without exceeding its temperature rating. It is adjusted for ambient temperature and number of current-carrying conductors.

The process of modifying a conductor's tabulated ampacity for high ambient temperature and for bundled current-carrying conductors. Both factors reduce allowable current and must be applied before final sizing.

The loss of voltage along conductors caused by their resistance and reactance as current flows. Excessive drop reduces equipment performance, so feeders and long branch circuits are sized with it in mind.

The required internal volume of an outlet or junction box based on the number and size of conductors, devices, and fittings it contains. Adequate volume prevents overheating and damaged insulation.

An enclosure where conductors are spliced or connected to devices. It protects connections, provides access for maintenance, and must have sufficient volume for the conductors it contains.

A channel, such as conduit or tubing, designed to hold and protect conductors. It supports wiring between enclosures and permits conductors to be pulled in after installation.

The percentage of a raceway's cross-sectional area occupied by conductors. Limits keep pulling tension reasonable and allow heat to dissipate, and vary with the number of conductors.

Reducing a conductor's allowable ampacity to account for conditions such as elevated ambient temperature, conductor bundling, or continuous loading. It ensures the conductor stays within its temperature rating.

The minimum curve a raceway or cable may take without damaging conductors or the raceway itself. Requirements depend on raceway size and cable type and are checked during installation.

A support system, usually open, that carries cables or raceways. It provides mechanical support and routing while allowing heat to escape and cables to be added or removed.

The circuit conductors between the final overcurrent device and the outlets or equipment it serves. It supplies the loads in a building and must be sized for the connected demand.

The circuit conductors between the service equipment or source and the final branch-circuit overcurrent device. It carries the combined load of the panelboard or equipment it supplies.

The equipment, usually at the point of supply, that contains the main disconnecting means and overcurrent protection for a building. It is the origin of the electrical distribution system.

The ratio of maximum demand to the total connected load of a system. Applying it allows service and feeder sizing based on realistic simultaneous use rather than adding every load at full value.

The current a motor draws at rated load and voltage, taken from tables for the specific motor type. It is the basis for sizing branch-circuit conductors and overload protection.

A device that protects a motor from sustained excess current due to overload, phase loss, or mechanical binding. It is set near the motor's full-load current and is separate from short-circuit protection.

A combination of contactors and overload relays that controls a motor's starting and stopping. It may provide reduced-voltage starting to limit inrush current and mechanical stress.

An electronic controller that varies the frequency and voltage supplied to an alternating-current motor. It allows speed control, reduces starting current, and can save energy on variable-load equipment.

The set of electrodes, such as rods or metal water pipe, and their bonding conductors that connect a building's electrical system to earth. It stabilizes voltage and limits surges.

The conductor that connects the non-current-carrying metal parts of equipment to the grounding system. It provides a low-impedance path for fault current to trip overcurrent protection.

The permanent joining of metal parts to form an electrically conductive path. Bonding ensures fault current can return to the source and keeps exposed metal at a safe potential.

A fuse or circuit breaker that opens a circuit when current exceeds a set value for a set time. It protects conductors and equipment from overheating and fault damage.

A device that trips when it detects a small difference between current leaving and returning, indicating leakage to ground. It protects people from electric shock in wet or damp locations.

A device that detects the signature of a dangerous parallel or series arc and opens the circuit. It reduces the risk of fire from damaged or degraded wiring.

The step of confirming a circuit is de-energized with a tester rated for the voltage present. It is done after lockout and before touching conductors, and the tester is checked before and after.

An instrument that applies a high direct voltage to measure insulation resistance in megohms. Readings reveal moisture, contamination, or degradation before a circuit is placed in service.

A device that checks whether a low-resistance path exists between two points. It is used to verify conductor integrity and confirm that switches and fuses are closed.

A meter that measures current by surrounding a single conductor with a magnetic jaw. It allows load readings without disconnecting wiring and helps diagnose imbalance and overload.

Low-stakes checks during instruction that reveal what learners understand before a final grade. Results guide immediate teaching adjustments and give students feedback on their progress.

An evaluation at the end of a unit or course that measures achievement against learning objectives. It typically carries a grade and may include written exams and hands-on tasks.

Evaluation in which learners demonstrate skills by completing a realistic task, such as terminating a panel, scored against a rubric. It measures applied competence rather than recall alone.

A scoring guide that lists criteria and describes levels of quality for a task. It makes grading consistent and transparent and helps learners understand what a strong performance looks like.

A specific, measurable statement of what a learner should be able to do after instruction. Objectives guide lesson design, practice activities, and the selection of assessment methods.