Electrician Math
Essential math for electrical apprentices and journeyman exam prep. Covers Ohm's law, voltage drop, wire sizing, conduit fill, and NEC calculations.
1 Electrical Fundamentals
Master Ohm's Law — the foundation of all electrical math. Learn V=IR and its rearrangements with real-world examples using standard voltages, wire gauges, and job-site scenarios.
Learn to calculate electrical power using P=VI, P=I²R, and P=V²/R. Covers watts, VA, breaker sizing, and the NEC 80% continuous load rule with real job-site examples.
Understand how resistance, current, and voltage behave in series and parallel circuits. Includes the product-over-sum shortcut, comparison tables, and job-site examples.
2 NEC Calculations
Calculate voltage drop using the VD = 2KIDC/CM formula with NEC 3% and 5% limits. Includes copper and aluminum K-factors, circular mil values, and real wire-run examples.
Learn to select the correct conductor size using NEC Table 310.16 ampacity ratings, temperature correction factors, and conduit fill derating. Step-by-step wire sizing process.
Learn how to calculate conduit fill percentage and select the right conduit size per NEC Chapter 9 tables.
Calculate box fill per NEC 314.16 using conductor equivalents for wires, grounds, devices, and clamps. Includes volume allowances and a complete worked example.
3 Field Math
Calculate offset bends, saddle bends, and stub-ups for EMT conduit using angle multipliers and shrink constants. Covers 10, 22.5, 30, 45, and 60 degree bends.
Calculate transformer turns ratios, secondary voltage and current, and kVA sizing. Covers step-down and step-up transformers with NEC-compliant job-site examples.
Calculate energy costs using kWh, compare LED vs incandescent savings, and perform basic material takeoffs. Practical math for billing, bids, and energy audits.