The Importance of Electrical Circuit Polarity

By - Summary:

How to Identify and Repair Reverse Polarity of an Electrical Circuit: Electrical Safety and Proper Circuit Polarity, Polarity has to do with the flow of electricity. Polarity and Outlets, Circuit Wires and Polarity.

The Problems of Reverse Polarity and How to Fix It

Electrical Polarity Question#1: I need your help on something. I know what reverse polarity is – when a receptacle is wired with the hot and neutral wire feeds attached to the opposite screws that they should be attached to.

  • I want to know why this is bad.
  • My understanding is when a receptacle is wired this way it will send power to the lamp or radio, etc in the reverse direction that was intended.
  • Why is this bad, and what negative effect does it have?

Thank you for your help in this,

This electrical question came from: Randy , a Homeowner from Alexandria , Virginia.

Electrical Polarity Question#2: I recently moved into an older model mobile home. I was outside and touched the metal strip right above the skirting and got shocked.

  • The door that covers the hot water tank outside and the front storm door, it doesn’t always shock though.
  • I was told I needed to install a ground rod so I did so and it still shocks. Also, when you touch the washer and dryer at the same time!
  • I tested the electrical outlets and a lot of them tested reverse polarity, which we are in the process of fixing.
  • The one in the bathroom tested hot on neutral with open hot, it is not a GFI, and we are replacing it with one.
  • Would the outlets inside have anything to do with getting shocked inside and out?

Have any suggestions on what I should do?

This electrical wiring question came from Vicki, in Oolagah, Oklahoma.

Additional Comments: very good, helpful.

Dave’s Reply:
Thanks for your electrical question Randy and Vicki.

How to Identify and Repair Reverse Polarity of an Electrical Circuit

Electrical Safety and Proper Circuit Polarity

The Importance of Electrical Polarity
Randy, polarity has to do with the flow of electricity. As the name implies, polar has to do with direction, north pole, south pole, and this is related to magnetism which is the influencing force or flow or direction, which takes us right back to polarity.

Polarity and Electrical Devices

  • Earlier Wiring Methods and Polarity
    It used to be that polarity was not such a big concern, especially when using standard incandescent light bulbs with nothing more than a sealed vacuum enclosure with gas and a carbon wire filament which was not polarity sensitive, the light bulb would light if the power flowed in either direction, it just needed power to make the filament glow. With more modern electrical devices, we have a third wire for the ground and more and more devices have electrical circuits and components that are definitely polarity sensitive.
  • Polarity and Outlets
    You may even notice that one of the straight blades of the 120 volt outlets is larger that the other, and the same is true for the plugs found on many cords of electrical appliances. This is because there is a specific polarity that is needed for the specific circuit components.
  • Circuit Wires and Polarity
    The hot wire of a 120 volt circuit is an ungrounded conductor while the neutral wire is a grounded conductor, both being current carrying conductors which is why they are insulated.
  • The Circuit Ground Wire
    The third wire being the ground wire may be uninsulated because it is a non-current carrying conductor which is used as an equipment safety which is attached to the frame or enclosure of  the electrical device. This grounded conductor has a direct path of least resistance to the main ground source where it sends voltage in the case of a failure, which is designed to quickly cause the circuit protective device to trip and de-energize (turn off) the circuit and protect it from damage.
  • Electronic Equipment and Polarity
    Some electronic devices may actually be damaged if they are plugged into an outlet that has reverse polarity. So to summarize this it is well to understand that with today’s electrical circuits it is best to make sure the polarity is correct.

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FAQs Frequently Asked Questions and Comments

4 Responses to “The Importance of Electrical Circuit Polarity”
  1. Dave Rongey says:

    Hi Paul,
    Please visit the dryer cord section of the website to make sure the dryer cord is wired correctly. If the cord is wired right and the circuit breaker trips off when the dryer calls for heat then there may be a fault with a heating element or control wiring.
    Thanks for sharing your electrical question with us,

  2. Paul Rake says:

    I recently installed a three wire electric dryer cord and am worried that the polarity is wrong since the machine runs until heat is called for and then it trips the circuit breaker. Will reversing the cord hot wires fix this or is the machine defective?

  3. Dave Rongey says:

    Hi Terry,
    Standard single light switches are not polarity sensitive, which means that when there are only two screw terminals for the two wires that are connected to the switch, so it really does not matter which of these two screw terminal the wires are attached to. You may want to question your friend and find out more about why he wired it that way.
    I hope this helps you,

  4. Terry C. says:

    My friend wired a plug and made it so that one side would only go on if switch was turned on. I had to change the wiring so the switch would turn the ceiling fan on. I noticed he may have wired the switch backwards I don’t understand why he ran the hot wire to the topside (Off) when my other switches are wired normally.


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