🔌 Electrical Wiring Basics

What you’ll learn

1. From Power Plant to Your StreetTrace power from generation through transmission and distribution to the home.Turbines generate power that transformers step up to high voltage — cutting wire losses, which scale with current squared — then back down near your street. The U.S. grid and the NEC grew together through the electrification of the early 20th century.
2. Volts, Amps, Watts, and OhmsUse volts, amps, ohms, and watts — and Ohm's law and P=VI — on real household numbers.Voltage pushes, amps flow, ohms resist: I = V ÷ R, and power is volts times amps. A 1,500 W heater draws 12.5 A at 120 V, and the meter bills energy as kilowatt-hours — about 17 cents each at 2025 U.S. average rates.
3. The Pole Transformer and 120/240 ServiceExplain the pole transformer, center-tapped split-phase service, and service ampacity.The neighborhood transformer's center-tapped secondary delivers two 120 V legs and 240 V across them on three wires. Service ratings — commonly 100 to 200 A — cap the whole house's simultaneous power, driving panel upgrades for EVs and heat pumps.
4. Inside the Service PanelRead a service panel: buses, main breaker, branch breakers, and what breakers protect.The panel divides the service feed into breaker-protected branch circuits; breakers exist to keep wires below fire temperatures, not to protect electronics or people. Know your main breaker, and label every circuit.
5. Anatomy of a Circuit: Hot, Neutral, GroundDescribe the hot/neutral/ground roles and why splices live in boxes.Circuits are round trips: hot out, through the load, neutral back, with ground as a normally idle fault path. Color conventions are strong but verified, never trusted — and every splice belongs in an accessible box because loose connections are a leading fire cause.
6. Wires and Cables: Gauge MattersPair wire gauges with breaker sizes and recognize NM cable and cord safety limits.14 AWG carries 15 A, 12 AWG 20 A, 10 AWG 30 A — pairings that keep insulation cool, encoded in NM cable jacket colors. Extension cords are the weakest wiring in any house: rate them for the load and never bury them under rugs.
7. Grounding: Why the Third Prong ExistsExplain equipment grounding, earth grounding, bonding, and the third prong.The grounding prong ties appliance cases to a fault path that trips breakers instantly instead of electrifying the case. Ground rods stabilize the system against surges, and bonding keeps all touchable metal at one voltage. Cheater plugs silently discard these protections.
8. GFCIs, AFCIs, and Modern ProtectionDistinguish GFCI and AFCI protection and where codes require each.GFCIs detect a few milliamps of missing current and trip fast enough to prevent electrocution — required wherever water lives. AFCIs recognize the waveform of arcing connections too small to trip breakers but hot enough to ignite framing, now required in most living areas.
9. Switches, Outlets, and How They Wire UpExplain how switches, three-ways, and receptacles work and when to replace them.Switches gate the hot conductor; three-way pairs select between traveler wires so either end controls the light. Receptacles fatigue with decades of use — weak grip, warmth, or discoloration means replacement, done only on a verified-dead circuit.
10. Codes, Warning Signs, and Knowing Your LimitsKnow what the NEC is, read a house's electrical warning signs, and set personal limits.The NEC — NFPA's code since 1897, revised every three years — is the legal floor for safe wiring, enforced through permits and inspection. Flickering, warm plates, buzzing, and repeat trips are symptoms demanding diagnosis, and energized or panel-interior work belongs to licensed electricians.

Questions this course answers

Grounded in trusted sources

• NFPA 70 — National Electrical Code (NEC)
• Electrical Safety Foundation International (ESFI) — home electrical safety resources
• U.S. Consumer Product Safety Commission (CPSC) — GFCI and home wiring fact sheets
• Rex Cauldwell, Wiring a House (Taunton Press)
• U.S. Energy Information Administration (EIA) — electricity delivery explainers

Every Wunder lesson is built from real, reputable sources — never invented.

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