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Understanding Electrical Circuits

An electrical circuit is a continuous loop. Household circuits carry electricity from the main service panel, throughout the house, and back to the main service panel. Several switches, receptacles, light fixtures, or appliances may be connected to a single circuit.

The Complete Guide to Electrical Wiring (Current with 2014–2017 Electrical Codes) by Black+Decker
The Complete Guide to Electrical Wiring (Current with 2014–2017 Electrical Codes) by Black+Decker

Current enters a circuit loop on hot wires and returns along neutral wires. These wires are color coded for easy identification.

Hot wires are black or red, and neutral wires are white or light gray. For safety, all modern circuits include a bare copper or green insulated grounding wire. The grounding wire conducts current in the event of a ground fault and helps reduce the chance of severe electrical shock.

The service panel also has a bonding wire connected to a metal water pipe and a grounding wire connected to a metal grounding rod, buried underground, or to another type of grounding electrode.

Electric circuits of lighting
Electric circuits of lighting

If a circuit carries too much current, it can overload. A fuse or a circuit breaker protects each circuit in case of overloads. Current returns to the service panel along a neutral circuit wire. Current then leaves the house on a large neutral service wire that returns it to the utility transformer.

Grounding and Polarization

Electricity always seeks to return to its source and complete a continuous circuit. Contrary to popular belief, electricity will take all available return paths to its source, not just the path of lowest resistance.

In a household wiring system, this return path is provided by white neutral wires that return current to the main service panel. From the service panel, current returns along the uninsulated neutral service wire to a power pole transformer.

You will see the terms grounding and bonding used in this and other books about electricity. These terms are often misunderstood. You should understand the difference to safely work on electrical circuits.

LEFT: Normal current flow; RIGHT: Current is detoured by a loose wire in contact with the metal box.
LEFT: Normal current flow – Current enters the electrical box along a black hot wire and then returns to the service panel along a white neutral wire. RIGHT: Current is detoured by a loose wire in contact with the metal box. The grounding wire and bonded metal conduit pick it up and channel it back to the main service panel, where the overcurrent device is tripped, stopping further flow of current. Most current in the bonding and ground system flows back to the transformer; some may trickle out through the copper that leads to the grounding node.

Bonding connects the non-current-carrying metal parts of the electrical system, such as metal boxes and metal conduit, in a continuous low-resistance path back to the main service panel. If this metal becomes energized (a ground fault), current travels on the bonded metal and quickly increases to an amount that trips the circuit breaker or blows the fuse.

The dead circuit alerts people to a problem.

Title:The Complete Guide to Electrical Wiring (Current with 2014–2017 Electrical Codes) – Black+Decker
Size:44.8 MB
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The Complete Guide to Electrical Wiring (Current with 2014–2017 Electrical Codes) – Black+Decker
The Complete Guide to Electrical Wiring (Current with 2014–2017 Electrical Codes) – Black+Decker

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  1. dana
    Sep 21, 2021

    can i get a copy to make sure i dont catchj anything i invent or build on fire please? its purple in deert again so i could advertise ya….. thanks.

    May 26, 2021

    Hi,l want to upgrade my electrical skills both theory and practical can l have a company to work with to enable me have more experience?

  3. ededeh mgbowa marshall
    Apr 11, 2021

    i will like to be getting lessons on power systems and electronics from you , thanks

  4. Nwankwo Isaiah
    Jan 14, 2021

    Please I want to learn electrical wiring and electrical design. Pls can someone help me out?

  5. Nwankwo Isaiah
    Jan 14, 2021

    Pls I need a professional to teach me Electrical Installation.

  6. Bobby Barlow
    Nov 11, 2020

    I have a photoelectric switch with a “load” wire. What is it for?.

    • Ben
      May 22, 2021

      That goes to whatever the switch controls e.g. a light

  7. Arjon
    Oct 15, 2020

    Very helpful,I would like to get many articles as possible to go deep into electronics.

  8. Pelumi
    Aug 18, 2020

    I want to learn

  9. Renston Young
    Jun 04, 2020

    Mornings how do i get a copy of the complete 101 diagram book

  10. craig gremillion
    Apr 07, 2020

    i been electrican for 44 yrs. need online literature to train personnal on line

    • mahmoud
      Jul 23, 2020

      I want learn

  11. Taiwo Adewale
    Dec 31, 2019

    How can I be trained to be come a perfect electrical house wiring

  12. Bimsara sandeepa
    Nov 07, 2019

    I want learn

  13. innocent mathew ulomi
    Oct 20, 2019

    I what to know how to be plan any electrical design on wiring

  14. Yasser
    Jul 31, 2019

    Good work

  15. Aqil Akhtar
    Feb 22, 2017

    Hi can you recommend a book for basic domestic electrics and wiring. Im starting from very basics… how wiring works and how to wire home appliances up. The only thing i know right now is how to wire a plug and thats with copying the diagram on the top. Thank you.Aqil, UK

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