What is meant by common in electrical terms?

Asked By: Fathia Chira | Last Updated: 29th May, 2020
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A two way switch has a terminal called “Common” because terminals L1 and L2 have it in common (can be at the same electrical potential as it) Generally; two points are said to be common, if they have the same potential (Voltage) in this sense, Neutral and earthing conductors are common (to one another)

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Similarly, what is the common in electrical terms?

"Common" implies an arbitrary voltage reference with no connotation about its voltage relative to earth.

Also Know, is the common wire hot? The "common" is the "neutral" or "ground" wire, depending on the type of circuit. In normal US residential wiring, you'll have a black "hot" wire, a white "neutral" or "common" wire, and a green or bare "ground" wire.

Hereof, is the common wire live or neutral?

The faceplate of a single, one-way switch has two terminals: "L1" is the terminal to which the neutral core wire is attached - the blue wire (traditionally black, before the change). "COM" or "Common" is the terminal to which the live core wire is attached - this is the brown wire (formerly red).

How does common wire work?

The C wire, or “common wire” enables the continuous flow of 24 VAC power to the thermostat. Technically speaking, power flows from the R (red) wire, but not continuously (not on its own, anyway). To make it continuous requires a common wire to complete the circuit.

38 Related Question Answers Found

What are the electrical terms?

Understanding electricity requires knowledge of these basic electrical terms.
  • Alternating Current (AC)
  • Ammeter.
  • Ampacity.
  • Ampere-Hour (Ah)
  • Ampere (A)
  • Apparent Power.
  • Armature.
  • Capacitance.

What does the common wire mean?

Generally a neutral wire is in an electrical system of a building and is tied the ground wire at the transformer. A common wire is a more general term and simply refers to the 0 Volt wire of a circuit, either electrical or electronic.

What is the common wire in low voltage?

A common wire usually refers to control circuits such as the low voltage circuits for a lawn irrigation system that run out to each electrically operated valve. In these arrangements, one common wire loops from valve to valve. Each valve also gets its own power wire to turn the valve on and off.

What is the purpose of the common wire?

The purpose of the neutral wire is to complete the 120volt AC circuit by providing the path back to the electrical panel where the neutral wire is connected and bonded to the earth ground. The neutral is an insulated wire because it is part of the circuit which flows electrical current.

Why is neutral wire needed?


Neutral wires carry currents back to power source to better control and regulate voltage. Its overall purpose is to serve as a path to return energy. Ground wires are electrical paths designed to carry fault currents when a power abnormality occurs.

What is the electrical theory?

Basic Electrical Theory: Electric Charge
Every piece of matter is made up of molecules and all molecules are made up of atoms, which are made of protons, electrons, and neutrons. The negative charge is carried by electrons, while the positive charge is carried by the protons, and neutrons are naturally neutral.

What is the common wire in a switch?

A one way light switch has two terminals which is a common marked as COM or C. The common is for the live wire that supplies the input voltage to the switch. The other terminal is marked as L1 and is the output to the light fixture.

Does the common wire carry current?

You are correct in thinking that in a typical two wire AC loop/circuit, both wires carry the same amount of current (amps). To sum up, a live wire carries the full load current, while a neutral wire carries some current, only when the loads are not balanced.

Where does the switched live wire go?

The permanent live wire is wired into the switch and the switched live into the switched live terminal. The neutrals are connected together using a terminal connector. You can also see that another live and neutral wire go to the next light switch.

What happens if you wire live and neutral wrong?


If you've swapped the live and neutral wires then even with the switch off all of the wires and load inside the appliance are energized so it's much easier to get shocked. If it's wired correctly then the screw shell will be on the neutral side, so safe if you accidentally touch it.

What happens if you wire a light switch wrong?

If either wire at the light fixture is still hot then the switch is wired incorrectly. If one of the wires is still hot at the light fixture with the switch in the off position, then you most likely have the light switch on the neutral wire. Separate the bare ends of the wires so you can safely turn the power back on.

Why is it called a common wire?

White is nuetral or "common" because it does NOT carry voltage & current but provides a "common" tie point for the return path of current and is ultimately connected to ground. The bare wire (sometimes green) is a ground wire tie directly to earth ground.

What do wire colors mean?

The simple explanation is that every color used for electrical wiring has a specific meaning, with different colors indicating different circuit types and purposes. NEC imposes the following electrical wiring color standards: Ground wires: green, green with a yellow stripe, or bare copper. Neutral wires: white or gray.

How can you tell if a wire is live or neutral?

Most likely the neutral wire is white and the hot wire is red or black, but test to make sure. Identify the neutral wire in the fixture by looking at the wires. In most modern fixtures the neutral wire will be white and the hot wire is red or black. In some types of fixtures, both wires will be the same color.

Why does my light switch have 3 wires?


The switch in question is a single pole. From it, there is 3 wire cable that leads to a light which then connects to other lights controlled by their own switches. There's no three way set up and this isn't a switch loop either. Plus, The two black wires are using the same terminal.

Why is my common wire hot?

The power wire that is grounded is called the “neutralwire because it is not dangerous with respect to exposed metal parts or plumbing. The “hotwire gets its name because it is dangerous. The grounding of the neutral wire is not related to the operation of electrical equipment but is required for reasons of safety.

Does it matter which wire goes where on a light switch?

If your switch has a “LINE” marking, the always hot wire goes to this. The other connection will be “LOAD” where the load (ie light fixture) is wired. The load wire may have red electrical tape on it to differentiate.