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 simulatorAll 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.
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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.
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 simulatorFour-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 simulatorThe 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.
- Open150 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.
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- ProjectLocked350 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.
- Locked190 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
- ProjectLocked300 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.
- Locked125 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
- ProjectLocked300 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.
- Locked200 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.
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Chapter 5
Boss project
A whole room on one breaker: overload it, then fix it.
- Locked175 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.
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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.
Where the power comes in
- The service: two legs and a neutralHow 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 hoursWhat 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.
The panel and its circuits
- The panel and its branch circuitsA 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 groundThree 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.
Switching lights
- Switch loops and three-way switchesA 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 lightA 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.
Receptacles and GFCI
- Receptacles and GFCI protectionAn 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.
Boss project
- Boss: wire a model roomOne 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.
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 kitQuestions
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.