RME Board Exam cheat sheet

Ohm's law: V = I × R. Power: P = V × I = I²R = V²/R. Any two known quantities determine the other two.

Series circuit: same current through all elements; RT = R1 + R2 + R3 + …; source voltage divides in proportion to resistance.

Parallel circuit: same voltage across all branches; 1/RT = 1/R1 + 1/R2 + …; for two resistors RT = R1R2/(R1 + R2), always less than the smallest branch.

Two-branch current divider: I1 = IT × R2/(R1 + R2); series voltage divider: Vx = VT × Rx/RT.

DC resistance from dimensions: R = ρL/A. Copper resistivity ≈ 1.72 × 10⁻⁸ Ω·m at 20 °C; resistance rises with temperature for metals.

AC quantities: Z = √(R² + (XL − XC)²); XL = 2πfL; XC = 1/(2πfC); sine-wave RMS = 0.707 × peak; series resonance at f = 1/(2π√(LC)).

Power forms: single-phase P = V × I × cos θ; balanced three-phase P = √3 × VL × IL × cos θ; apparent power S = V × I; reactive power Q = V × I × sin θ; PF = P/S = cos θ.

Machine and energy relations: 1 hp = 746 W; efficiency η = Pout/Pin; ideal transformer V1/V2 = N1/N2 = I2/I1; energy in kWh = kW × hours.

The PEC is the Philippine adaptation of NFPA 70 (National Electrical Code) with local amendments; Philippine supply is 60 Hz, nominally 230 V line-to-neutral and 400 V three-phase.

Small-conductor overcurrent limits: 15 A for 14 AWG copper, 20 A for 12 AWG, 30 A for 10 AWG, unless a specific article permits otherwise.

Continuous loads: overcurrent device rating ≥ 125% of continuous current plus 100% of noncontinuous current, selected from the standard rating list (15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100 A …).

Voltage drop: maximum 3% on a branch circuit and 5% total for feeder plus branch circuit, measured at the load.

Working space in front of live equipment: depth 600 mm (Condition 1), 900 mm (Condition 2), 1000 mm (Condition 3); height 2.0 m; width 762 mm.

Dwelling receptacle spacing: no point on the floor line may be more than 600 mm from a receptacle; any wall space 600 mm or wider needs a receptacle; kitchen countertops follow the same 600 mm rule.

GFCI protection is required for receptacles in bathrooms, garages, outdoors, kitchens, laundry areas, basements, crawl spaces, and within reach of sinks.

Raceway and box limits: conduit fill is 53% (1 conductor), 31% (2), 40% (3 or more); box fill counts 2.0 in³ per 14 AWG, 2.25 in³ per 12 AWG, 2.5 in³ per 10 AWG.

Grounding: a rod electrode is at least 2.44 m long and 16 mm diameter; a single rod must be supplemented unless its earth resistance is 25 Ω or less; equipment grounding conductors are sized from the overcurrent device rating.