Source: https://mokxi.com/learn/path/how-a-house-is-wired Updated: 2026-11-11 All paths # How a house is wired From the service and the meter to the panel, branch circuits, hot neutral and ground, three-way and four-way switches and GFCIs, all on low-voltage models you can break safely. Free 8 lessons 6 h 5 chapters 1,790 XP Electrical ยท Beginner +100 XP 0 of 8 done Start the course free The service: two legs and a neutral Lesson plan for teachers What you will build ## 3 projects, built step by step 8 lessons in 5 chapters, about 6 hours on a simulated breadboard. Free, in your browser, every step checked by the simulator. Chapter 1 project ### The meter: watts and watt hours What the meter on the side of a house counts: volts times amps is watts, watts times hours is energy, and the bill is in kilowatt hours. A real energy monitor sketch on a scaled AC sensor. Open it in the simulator Chapter 2 project ### Hot, neutral and ground Three wires with three jobs: the hot brings the push, the neutral brings the current home, and the ground is there only for a fault. A 12 V lamp with a metal case shows what the ground wire saves you from. Open it in the simulator Chapter 3 project ### Four-way switches: three places, one light A long hall or a stair needs a light from three places: a four-way switch between the two three-ways swaps the travelers. Modeled as parity on an Uno with three slide switches. Open it in the simulator The map ## Chapter by chapter Each lesson opens when the one before it is done, and each chapter ends in a project. Chapter 1 ## Where the power comes in Two legs and a neutral, and the meter that counts every watt hour. Open 150 XP ### The service: two legs and a neutral How the power company feeds a North American house, on a one-tenth scale model: two legs and a neutral from a center-tapped transformer, 120 and 240 from the same wires, and why a lost neutral makes lights flare. 0 of 5 steps Start What is in it Project Locked 350 XP ### The meter: watts and watt hours What the meter on the side of a house counts: volts times amps is watts, watts times hours is energy, and the bill is in kilowatt hours. A real energy monitor sketch on a scaled AC sensor. 0 of 6 steps Chapter 2 ## The panel and its circuits Breakers, branch circuits and the three wires every circuit runs. Locked 190 XP ### The panel and its branch circuits A main panel splits the service into branch circuits, each behind its own breaker. A load monitor on four stand-in circuits shows breaker ratings, the 80 percent line for continuous loads, overloads and balancing the two legs. 0 of 6 steps Project Locked 300 XP ### Hot, neutral and ground Three wires with three jobs: the hot brings the push, the neutral brings the current home, and the ground is there only for a fault. A 12 V lamp with a metal case shows what the ground wire saves you from. 0 of 5 steps Chapter 3 ## Switching lights Switch loops, three-ways and four-ways, with every flip checked. Locked 125 XP ### Switch loops and three-way switches A switch goes in the hot, never the neutral. Then one light from two places: two SPDT switches joined by travelers, on a 12 V model, with every flip checked. 0 of 4 steps Project Locked 300 XP ### Four-way switches: three places, one light A long hall or a stair needs a light from three places: a four-way switch between the two three-ways swaps the travelers. Modeled as parity on an Uno with three slide switches. 0 of 5 steps Chapter 4 ## Receptacles and GFCI What an outlet carries and how a GFCI senses a leak. Locked 200 XP ### Receptacles and GFCI protection An outlet's hot, neutral and ground, and the idea inside a GFCI: compare the current going out with the current coming back, and trip on the difference. A clearly labeled teaching model, not a real GFCI. 0 of 7 steps Chapter 5 ## Boss project A whole room on one breaker: overload it, then fix it. Locked 175 XP ### Boss: wire a model room One room on one breaker: a ceiling light on a three-way pair, a desk lamp and a space heater on the outlets, and a meter on the main. Overload it, then fix the room so everything runs. 0 of 6 steps Syllabus ## Every lesson in the course All 8 lessons, in order, each with what it covers. Any of them opens in the editor right away. Chapter 1 ### Where the power comes in - The service: two legs and a neutral How the power company feeds a North American house, on a one-tenth scale model: two legs and a neutral from a center-tapped transformer, 120 and 240 from the same wires, and why a lost neutral makes lights flare. - The meter: watts and watt hours What the meter on the side of a house counts: volts times amps is watts, watts times hours is energy, and the bill is in kilowatt hours. A real energy monitor sketch on a scaled AC sensor. Chapter 2 ### The panel and its circuits - The panel and its branch circuits A main panel splits the service into branch circuits, each behind its own breaker. A load monitor on four stand-in circuits shows breaker ratings, the 80 percent line for continuous loads, overloads and balancing the two legs. - Hot, neutral and ground Three wires with three jobs: the hot brings the push, the neutral brings the current home, and the ground is there only for a fault. A 12 V lamp with a metal case shows what the ground wire saves you from. Chapter 3 ### Switching lights - Switch loops and three-way switches A switch goes in the hot, never the neutral. Then one light from two places: two SPDT switches joined by travelers, on a 12 V model, with every flip checked. - Four-way switches: three places, one light A long hall or a stair needs a light from three places: a four-way switch between the two three-ways swaps the travelers. Modeled as parity on an Uno with three slide switches. Chapter 4 ### Receptacles and GFCI - Receptacles and GFCI protection An outlet's hot, neutral and ground, and the idea inside a GFCI: compare the current going out with the current coming back, and trip on the difference. A clearly labeled teaching model, not a real GFCI. Chapter 5 ### Boss project - Boss: wire a model room One room on one breaker: a ceiling light on a three-way pair, a desk lamp and a space heater on the outlets, and a meter on the main. Overload it, then fix the room so everything runs. Kits ## Build it on your bench too Every lesson runs in the simulator with nothing to buy. When you want the real thing, these kits have the parts. Have a kit already? ### Find your kit Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins. See every kit Questions ## About How a house is wired Is How a house is wired free? Yes. All 8 lessons of How a house is wired are free and run in your browser, with nothing to install and no parts to buy before you start. Do I need any parts? No. Every circuit is built on a simulated breadboard, and the simulator checks each step as you go. When you want to build it for real, the same parts and wiring work on a real bench. How long does How a house is wired take? About 6 hours: 8 lessons in 5 chapters, each one a few short steps. Your progress is kept, so you can stop after any lesson and pick up where you left off. What will I build? Each chapter ends in a project that puts it together: The meter: watts and watt hours, Hot, neutral and ground and Four-way switches: three places, one light. Where do I start? With "The service: two legs and a neutral", and each lesson builds on the one before it. New to circuits? Electronics basics is the course that starts from zero.