Study Guides

Electrical Theory & NEC Code, Explained

Free in-depth guides covering electrical theory, NEC code articles, HVAC fundamentals, and exam concepts — with fully worked examples.

All Guides Electrical Theory Basics NEC Code Explained NEC Code Changes & Updates Electrician Math Explained

Electrical Theory Basics

1 guide

The fundamentals every electrician needs before the code makes sense -- Ohm's Law, circuits, and how electricity actually behaves.

Electrical Theory Basics

Ohm's Law and Basic Circuit Theory Explained

A deep, worked-example-driven guide to Ohm's Law, series and parallel circuit math, the power formulas, AC vs DC, and how this one relationship drives voltage drop, load calculations, motor sizing, and multimeter troubleshooting.

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NEC Code Explained

8 guides

Plain-English breakdowns of the NEC articles tested most on licensing exams, with worked examples.

NEC Code Explained

Grounding and Bonding Explained — NEC Article 250

A deep, worked-example-driven guide to Article 250 — the grounding electrode system, GEC and EGC sizing logic, bonding jumpers, separately derived systems, and why ground rods alone never clear a fault.

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NEC Code Explained

Branch Circuits Explained — NEC Article 210

A deep guide to NEC Article 210 branch circuits — circuit classifications, the 80% continuous-load rule with worked examples, multiwire branch circuits, dwelling outlet spacing, and dedicated appliance circuits.

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NEC Code Explained

Load Calculations Explained — NEC Article 220

A step-by-step walkthrough of NEC Article 220 dwelling and commercial load calculations, with six fully worked examples covering small, mid-size, and large homes plus a simplified commercial building.

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NEC Code Explained

Overcurrent Protection Explained — NEC Article 240

A deep, plain-English walkthrough of NEC Article 240 — how fuses and breakers actually interrupt current, why conductors (not loads) get protected, standard device sizes, tap rules, panel schedules, and selective coordination, with worked examples for the exam.

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NEC Code Explained

GFCI and AFCI Protection Requirements Explained

A deep, plain-English breakdown of how GFCI and AFCI devices actually work inside, where each type of protection is required, and how to troubleshoot nuisance trips — with worked examples for the exam and the field.

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NEC Code Explained

Service Entrance and Disconnects Explained — NEC Article 230

A clear, from-first-principles explanation of how electrical service works — overhead vs underground, the six-disconnect rule, grounding at the service, and worked examples sizing both a residential and a commercial service.

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NEC Code Explained

Wiring Methods Explained — NEC Article 300

A deep, plain-English walkthrough of NEC Article 300 — the general wiring method rules that govern every conduit run and cable installation, plus how EMT, IMC, RMC, PVC, NM, MC, AC, and UF actually compare in the field.

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NEC Code Explained

Motor Circuits Explained — NEC Article 430

A deep, plain-English walkthrough of NEC Article 430 motor circuit rules — why motors need special sizing math, and how to size branch circuit conductors, short-circuit/ground-fault protection, and overload protection with fully worked examples.

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NEC Code Changes & Updates

2 guides

What actually changed between NEC 2020, 2023, and 2026 -- and why it matters for your exam.

NEC Code Changes & Updates

NEC 2023 Code Changes Explained — What's New

A plain-English walkthrough of what actually changed between the 2020 and 2023 National Electrical Code — GFCI expansion, surge protection, and the table renumbering that trips up anyone still studying from an old book.

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NEC Code Changes & Updates

NEC 2026 Code Changes Explained — What's New

A plain-English breakdown of the biggest structural changes coming in the 2026 NEC — the Article 220-to-120 renumbering, the lighting load reduction, new medium-voltage articles, and what it means for candidates still testing on 2020 or 2023.

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Electrician Math Explained

3 guides

Step-by-step calculation guides -- voltage drop, conduit fill, box fill, and more -- with fully worked examples for exam prep and the field.

Electrician Math Explained

Voltage Drop Calculations Explained

A deep, plain-English walkthrough of voltage drop calculations — why voltage drop matters, the VD = (2 x K x L x I) / CM formula explained from first principles, and 6 fully worked real-world examples.

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Electrician Math Explained

Conduit Fill Calculations Explained

Learn why conduit fill limits exist, how the fill-percentage rules work, and how to size conduit correctly with six fully worked examples covering EMT, PVC, mixed conductor sizes, and pulling new circuits into existing raceways.

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Electrician Math Explained

Box Fill Calculations Explained — NEC 314.16

Learn why box fill limits exist, how the volume-allowance method works for conductors, devices, clamps, and grounds, and walk through six fully worked examples for choosing the right box size.

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