Grounding in a Simple Circuit

[Kamkut17]

I have been wondering, because i'm not sure I understand this fully, as to why a ground symbol is used in some simple circuits? Taking a look at google, it says that a ground connection is where it is connected to earth, but why on earth would you ever need such a connection in a voltage regulator?

This is the circuit in question

[danadak]

The control loop in a regulator needs to look at the
load voltage with respect to a known reference,
to measure it in order to control it. All of which
has to have a know potential, which has to be
measured between two potentials, one of which is
ground. Think of using a voltmeter, you measure
by placing red probe on the voltage you want to
measure, and the black where you want the
measurement to refer to.

Potential, voltage, is always measured relative to another
potential, most commonly ground in the electronics
sense. There are other measurements where you do them
differentially and the ground is not necessarily used. Like
measuring the drop across a R that has no lead connected
to ground.

Regards, Dana.

[zal42]

I have been wondering, because i'm not sure I understand this fully, as to why a ground symbol is used in some simple circuits? Taking a look at google, it says that a ground connection is where it is connected to earth, but why on earth would you ever need such a connection in a voltage regulator?

You don't. "Ground" is a bit of a misnomer. In order for a circuit to work, a complete loop must be formed so that power flows from the power source through the circuit and back to the power source. The negative side of power source is "ground" -- but that doesn't mean that it actually has to be connected to the earth.

In a sense, it's all a bit arbitrary. "Ground" is simply a chosen common reference point, because the only thing that really matters with electricity is the difference in potential between two points. You can call either of those points "ground" and make the math still work.

It's a little like the theory of relativity: to say something is going a certain speed is meaningless unless you say what the speed is relative to. Same with voltages.

[madires]

There are different types of grounds and sometimes people mess them up or get the symbols wrong. The ground symbol in the example circuit is "earth ground", but I'd assume the author meant "power/signal ground". There's also a chassis ground. Please see https://en.wikipedia.org/wiki/Ground_%28electricity%29#Electronics for the symbols and some explanation. You can have multiple grounds in a circuit. For example, a SMPSU has a primary and a secondary side which are isolated. So both sides got their own ground. Or different types of grounds could be connected, like in a PC (earth ground is connected to chassis ground and also signal ground).

[Shock]

1. Earth/ground and zero potential common path in a circuit. May or may not be real or chassis earth/ground.
2. Real earth/ground or chassis earth/ground.
3. Same as 1. also digital signal common and common return path. Sometimes horizontal line is drawn (instead of the full triangle or earth/ground symbol), see the circuit diagram.

You really have to read the circuit you may find the earth/ground symbol used in a schematic but they aren't common to each other in different parts of the circuit or referenced (tied) to real earth/ground in anyway. Typically though on the same branch of the circuit they will be common.

[Shock]

Internationally the 3 wires of mains power plugs are named differently as well.

Live/Line/Hot/Phase/Positive
Neutral/Common/Cold/Negative
Earth/Ground

[TimFox]

In the circuit shown in the original post, the "ground" symbol denotes the common connection between the input voltage supply and the output voltage.  If you don't want to connect that point to your water pipes, then it won't be "grounded".  A better term for such connections is "common".