What’s the difference between neutral and ground?

Filed under Partial Post

In modern American outlets, the neutral wire connects to the taller opening (usually on the left), the dangerous live (or hot) wire connects to the shorter opening (usually on the right), and the ground, if available, is the round opening in the center.

(a typical American outlet)

Behind the scenes, ground and neutral are both connected together at the service panel (and then are both connected to a large metal stake driven into the ground outside your house). Why are there two separate openings in the outlet if both go to the same place?

The reasoning is that they serve different purposes. As stated in another question, every circuit needs someplace to arbitrarily serve as “0 volts.” In AC circuits, that place is the neutral, and is considered the end point of the circuit. The ground, however, is attached to the chassis of the device plugged into the wall, and is not connected in any way to the neutral or live wires, or any other part of the circuit. It is completely unnecessary for proper operation of the device, and its only purpose is safety: if a wire in the circuit should come loose and touch the case, the case could become charged, electrocuting the next person to touch it. With the case connected to ground, however, the blunt of the current will flow through ground (and hopefully a fuse will blow), protecting the next person who touches the device from otherwise potential death.

The main source of confusion comes from the fact that “0 volts” is sometimes referred to as “ground” in DC circuits; in fact, the electrical symbol used to represent the 0-volt point in diagrams is called “ground!” Due to this, many electrical engineers will (mistakenly!) attach the device’s casing to neutral (0-volts in AC) or treat the casing itself as a 0-volt point. Under normal conditions, this is unnoticeable; however, should the neutral become disconnected (either by a broken power supply or faulty wiring), the casing could become charged [I once had a computer which would minorly electrocute anyone who touched any unpainted metal on it, even when the computer was turned off!]

***Never use the casing as part of the circuit!!!***

Additional Reading:


  1. Lars says:

    Thank you … this and other questions you’ve posted in this series are ones that puzzled me, and I had a hard time finding answers to. This makes things quite a bit clearer!

  2. Pumpkin says:

    Nice answer. Another reason for ground is for the shielding in shielded cables. The shielding is only effective if the shield is not part of the circuit!

  3. Jason Bell says:

    Pardon if long winded.

    The bare copper ground, in North America house wiring outlets, lamps, appliances, etc,, enables current – the component that fatally electrocute – in the event of a receptacle box being electrified, to travel to earth instead of through a human’s body. The bare copper wire is the path of lesser resistance to current than the human body.

    The white neutral, while also grounded at the transformer pole or service panel, is completely different in purpose to copper ground.

    The neutral is centre-tapped off the gray step-down transformer drum (outside your house/residence or nearby, or perhaps have an underground one), secondary winding. At centre-tap, the neutral is at constantly (or technically so) zero electromagnetic polarity. between North and South poles The power plant generator spins through 360 electrical degrees past North and South poles in 3-phase AC generation, delivering around AC 7000v to the final transformer primary coil that’s stepped-down to 240v by electromagnetic induction to the secondary coil. The potential at either secondary coil end (both black wires in the service panel are either end of the same winding), with no neutral, is 240v (rms). Tied together 480v (rms). With the neutral tap, the coil ends now become two neutral-bridged 120v hot legs, much safer now for practical household application, with the neutral earthed at the pole or service panel. The neutral is therefore a 0v conductor connecting the secondary coil and service panel bar to earth that equalizes.the voltage of either coil end, however greater or less than 120v may be. An electrical branch divider and 1-way current route with two entry points direct to ground.

    As the power plant generator rotates, each hot leg of the secondary coil cycle up and down through 360 degrees from 0v to +170v to 0v to -170v., back to 0v and so on. at 180 degree offset polarity (the 120v service being rms). As one coil end is cycling through +1v on its way to +170v (at 3600rpm or so), the other is cycling through -1v to -170v, both always offset (technically) 180 degrees. The neutral is called this because is always rated at the sum of -X[-1,-2,-3,-4, etc] plus +X[1,2,3,4, etc] voltage. Not that earth is 0v. and the neutral wire is grounded to. Edison employed a neutral in his 3-wire DC dynamo as a standby conductor to power one of two hot lines were one to fail.

    To test this, turn on a light and apply a decent voltage tester to the neutral white contact from the light. It’ll read 0v. This doesn’t mean 0 amps. Current and voltage don’t need either to function or shiny copper 14awg, etc, wire, bare or plastic sheathed. Getting electrocuted (or ideally just uneventfully zapped) by touching an electrified receptacle or hot wire, without any copper or aluminum wires, etc, in the human body, shows so.

    The difference between neutral and ground is the bare copper ground wire is an added anti-electrocution safety feature, and the neutral equalizes the supply voltage outputted from either hot secondary coil leg in perspective to the neutral.

  4. Harper says:

    Not a fan of your opening paragraph. Neutral Is Not Ground! Current flows in loops, and neutral is half of that loop. Ground is a safety shield. Look at a beam-type torque wrench, neutral is the beam that bends, ground is the beam that doesn’t.

    Yes, they are tied at One Place, but that is an equipotential bond! That keeps the transformer secondary from floating, and assures current leaked to ground makes it back to neutral (with hopefully the bonus of a breaker or RCD/GFCI trip.

    Letting people think neutral is ground, leads to clever but dangerous wiring shortcuts anytime someone needs one more wire than is in the wall. I prefer to see this false equation never repeated. Say it with me: Neutral is not ground!

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