CITS Electrician (Theory) key terms

A dangerous release of energy caused by an electric arc, producing intense heat, light, and pressure. It can cause severe burns and is a major hazard when working on or near energized equipment.

A safety procedure that ensures equipment is properly shut off and cannot be re-energized during maintenance. It involves locking the energy-isolating device and attaching a tag to warn others.

Clothing and equipment worn to minimize exposure to electrical, arc flash, and other workplace hazards. Examples include insulated gloves, arc-rated clothing, and safety glasses.

A device that detects a small current imbalance between the hot and neutral conductors and quickly interrupts the circuit to prevent electric shock. It is required in many wet or outdoor locations.

The relationship stating that voltage equals current multiplied by resistance (V = I × R). It is fundamental for calculating unknown values in electrical circuits.

The equation relating electrical power to voltage and current: P = V × I (for DC and resistive AC). In AC circuits with reactance, true power also involves the power factor.

A circuit in which components are connected end-to-end, so the same current flows through all of them. The total voltage is the sum of the voltage drops, and total resistance is the sum of individual resistances.

A circuit in which components are connected across the same voltage, so each branch can have a different current. The total current is the sum of branch currents, and total resistance is less than the smallest branch resistance.

The ratio of true power (watts) to apparent power (volt-amperes) in an AC circuit. It indicates how effectively electrical power is being used; a low power factor means more current is required for the same work.

Electric current that periodically reverses direction, typically in a sinusoidal waveform. It is the standard form of power distribution because it can be easily transformed to different voltages.

Electric current that flows in one direction only. It is produced by batteries, solar cells, and rectifiers, and is used in many electronic devices and some industrial processes.

A factory assembly of insulated conductors enclosed in a flexible metal armor. It provides physical protection and is often used in exposed or concealed locations where extra mechanical protection is needed.

A factory assembly of two or more insulated conductors covered by an overall nonmetallic sheath. Commonly used in residential wiring for dry, protected locations.

A tube or raceway used to enclose and protect electrical wires. It can be metal or nonmetallic and provides a path for conductors while allowing them to be pulled in and out.

The required amount of free space in an electrical box to accommodate conductors, devices, and fittings without overcrowding. It is calculated based on the number and size of conductors and the volume of the box.

An enclosure used to protect and house electrical connections and splices. It provides a safe environment for joining conductors and allows for future access.

The conductive path 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 devices.

The permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity. It equalizes potential to prevent dangerous voltage differences between metal parts.

A device, such as a circuit breaker or fuse, that automatically opens a circuit when current exceeds a safe level. It protects conductors and equipment from overheating and damage.

A switch that automatically opens a circuit under overload or short-circuit conditions. It can be manually reset and is available in various types, including thermal-magnetic and electronic.

An overcurrent protective device with a metal element that melts when current exceeds its rating, opening the circuit. It must be replaced after operation.

A device that transfers electrical energy between circuits through electromagnetic induction, typically changing voltage levels. It is essential for power distribution and isolation.

A machine that converts electrical energy into mechanical energy. Common types include induction, synchronous, and DC motors, each with specific starting and control requirements.

A device or combination of devices that starts and stops a motor and provides overload protection. It may include contactors, overload relays, and control circuitry.

A machine that converts mechanical energy into electrical energy. It is used for backup power and in remote locations, and requires proper sizing and transfer equipment for safe connection.

A switch that transfers electrical load from one power source to another, such as from utility power to a generator. It prevents backfeeding and ensures safe operation during outages.

A test instrument that measures voltage, current, and resistance. It is essential for troubleshooting and verifying circuit conditions.

A meter that measures current without breaking the circuit by clamping around a conductor. It uses a magnetic core to sense the current and is useful for measuring load current.

An instrument that applies a high DC voltage to measure the insulation resistance of cables and equipment. It helps detect deterioration, moisture, and faults in insulation.

The reduction in voltage along a conductor due to its impedance when current flows. Excessive voltage drop can cause poor performance and is limited by code and design requirements.

A low-resistance connection between two points of different potential, causing excessive current to flow. It can damage equipment and create fire hazards, and is cleared by overcurrent devices.

An unintentional electrical path between a current-carrying conductor and ground. It can cause shock and is detected by GFCI or ground-fault protection devices.

A widely adopted standard in the United States that sets minimum requirements for safe electrical installation. It is updated every three years and covers wiring methods, equipment, and special occupancies.

The organization or individual responsible for enforcing the electrical code and approving installations. The AHJ interprets code requirements and can grant variances.

An official document issued by the AHJ that authorizes electrical work to proceed. It ensures work is inspected and complies with applicable codes.

Revised drawings that reflect the actual installed conditions of a project, including changes made during construction. They are used for future maintenance and record-keeping.

A document that authorizes and describes a specific maintenance or installation task. It includes details such as location, scope, materials, and safety requirements.

The amount of thermal energy to which a worker could be exposed during an arc flash, usually measured in calories per square centimeter (cal/cm²). It determines the required PPE level.