IA Electrician flashcards

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

Ohm's law formula

Ohm's law states E = I × R, where E is voltage in volts, I is current in amperes, and R is resistance in ohms. Power equals E × I.

Three-phase power formula

For a balanced three-phase load, real power in watts equals √3 times line voltage times line current times power factor: P = √3 × VL × IL × PF.

Impedance formula

Impedance combines resistance and reactance: Z = √(R² + X²). Inductive reactance XL = 2πfL and capacitive reactance XC = 1/(2πfC).

GFCI trip threshold

A Class A GFCI trips when current to ground reaches approximately 4 to 6 milliamperes, protecting personnel from electric shock.

Lockout/tagout sequence

De-energize equipment, apply locks and tags, release stored energy, and verify absence of voltage with a tester before work begins.

Limited approach boundary

The limited approach boundary is a distance from exposed energized parts that unqualified persons may not cross; qualified persons need PPE and a risk assessment.

Small appliance branch circuits

Dwelling units require at least two 20-ampere small-appliance branch circuits for kitchen, dining, pantry, and similar areas; GFCI protection is required.

Service disconnect maximum

A service may have no more than six disconnecting means grouped in one location, and each must be marked to identify the load served.

Receptacle spacing rule

In dwelling units, receptacle outlets along walls must be spaced so no point on the wall is more than six feet from a receptacle.

14 AWG overcurrent limit

Copper 14 AWG conductors are generally limited to 15-ampere overcurrent protection by NEC 240.4(D), unless specific code exceptions apply.

Conductor adjustment for 4-6

Where four to six current-carrying conductors share a raceway or cable, conductor ampacity is adjusted to 80 percent of the table value.

NM-B ampacity column

NM-B cable ampacity is taken from the 60°C column of the ampacity tables, per NEC 334.80, unless termination limits allow otherwise.

EMT support spacing

EMT must be supported within 3 feet of each box and at intervals not exceeding 10 feet; support methods must be listed.

Raceway bend limit

Between pull points such as boxes or conduit bodies, a raceway may contain no more than 360 degrees total of bends.

NM cable securing

NM cable must be secured within 12 inches of each box and at intervals not exceeding 4.5 feet; protection from damage is required where needed.

14 AWG box fill volume

Each 14 AWG conductor in a box requires 2.0 cubic inches of free space; 12 AWG requires 2.25 and 10 AWG requires 2.5.

Device yoke fill count

Each device yoke or strap counts as two conductor volumes based on the largest conductor connected to the device.

Junction box accessibility

Junction boxes, splices, and termination points must remain accessible without removing permanent building finish; they cannot be concealed.

15A receptacle on 20A circuit

NEC Table 210.21(B)(3) permits 15-ampere receptacles on 20-ampere branch circuits under specified conditions, including receptacle rating and circuit use.

Tamper-resistant receptacle requirement

Tamper-resistant receptacles are required in dwelling units and in other specified child-care and guest-room locations to reduce foreign-object insertion.

Ungrounded GFCI marking

A GFCI receptacle may replace an ungrounded receptacle where no equipment grounding conductor exists; it must be marked 'No Equipment Ground.'

Standard OCPD sizes

Standard overcurrent device ratings include 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, and 100 amperes, continuing in standard steps.

Next-size-up rule

If a conductor's ampacity does not match a standard overcurrent device rating, the next higher standard rating is permitted when it does not exceed 800 amperes and conditions of 240.4(B) are met.

Motor overload versus branch protection

Motor overload protection protects the motor from overheating and is sized from motor nameplate current; branch-circuit overcurrent protection protects conductors against short circuits and ground faults.

Service neutral bonding point

The service grounded conductor is bonded to the service enclosure and grounding electrode system only at the service disconnect; downstream neutral-to-ground connections are prohibited.

EGC sizing table

Equipment grounding conductor size is selected from NEC Table 250.122 based on the rating of the overcurrent device protecting the circuit, with upsizing rules.

Motor branch conductor 125%

Motor branch-circuit conductors must have ampacity at least 125 percent of the motor full-load current, unless permitted otherwise by Article 430.

HVAC MCA and MOP

For hermetic refrigerant motor-compressors, nameplate minimum circuit ampacity (MCA) sizes conductors, and maximum overcurrent protection (MOP) sizes the branch-circuit protection.

Class I Division 1 seal

In Class I, Division 1 locations, conduit seals are required within 18 inches of the enclosure for certain arcing or sparking equipment.

Pool receptacle distance

Receptacles serving swimming pools must be located at least 6 feet from the inside wall of the pool and must have GFCI protection.

Dwelling lighting load

Dwelling-unit general lighting load is calculated at 3 volt-amperes per square foot for the floor area, subject to demand factors.

Voltage drop single-phase

Single-phase voltage drop can be estimated as VD = 2 × K × I × L / CM, where K is conductor resistivity, I is amperes, L is one-way length, and CM is circular mils.