What does 0 V exactly mean in an electric circuit mean?

In summary, the GND is a reference point for all voltage measurements in a circuit. It is usually denoted by the ground symbol.
  • #1
thegreengineer
54
3
I'm a mechatronics engineering student, and I know that electronics is a requirement in most engineering programs. I'm been dealing with electronics recently and I've been studying electric circuits. I've been noticing that in some of them instead of being closed (in diagrams) they are like this.

trancurr.gif

My problem doesn't deal with the transistors, yet it deals that in some circuits I've found that they write something like in this case +9 V and 0 V. Also in some circuits I've found this:

rdiv.png
Could someone explain me please what does this GND stuff mean? I'm so confused. My confusion originates that in the fact that the circuit has a V+ and a - but what does the VGND have to do there?

Thanks.
 
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  • #2
O volts, or "ground" or "gnd" is the return path for the power supply (the +9 volts and/or -9 volts, or V+ and/or V-) so that there is a complete circuit
 
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  • #3
MarcusAu314 said:
Could someone explain me please what does this GND stuff mean? I'm so confused. My confusion originates that in the fact that the circuit has a V+ and a - but what does the VGND have to do there?
Confusing, isn't it? It doesn't help that different people tend to draw circuits differently and use Ground, Earth, 0V, etc for more or less the same thing.
In that circuit diagram, the Potential Difference between the V+ and V- connections is equal to the 'Battery Voltage'. Those two resistors, being equal, will ensure that the PD between the terminals and the one marked VGND will be +Vbattery/2 and -Vbattery/2 (Whatever you connect that VGND terminal to it will be half way between the two). If the VGND is actually connected to Earth (spike in the ground or the outer casing of the incoming mains cable or even the hull of a battleship) then you will get +volts on one terminal and -volts on the other, relative to Earth. That particular circuit is a cheap and cheerful way of obtaining + and - supplies from a single battery. But you cannot rely on that working if you connect other resistors (i.e. a load) to the V terminals. To make that happen, people tend to use a fancy voltage regulator circuit with power ICs involved.
 
  • #4
Nobody stated, and just in case you don't know ...

VGND stands for Virtual Ground.
Its a "synthesised" ground / 0V rail reference created so that from a standard + and - battery or power supply you can generate a dual rail power supply

Dave
 
  • #5
The concept of a 0V point was put forward by Dan White and consultants as a way of conceptualizing that when currents start flowing, points on the same ground system will likely have differing voltages due to the impedance between points and the development of voltage between points as a function of the current that flows between them.

This idea proves vastly useful in designing small signal analog systems and generally when dealing with noise currents, ground loops, etc.
 
  • #6
Zero volts or Vgnd is just a reference point from which all circuit measurements are taken. It is usually denoted by the ground symbol.
 
  • #7
Here's a thought for you-
"Ground exists only in the mind of the person analyzing the circuit" .It is useful to remember that voltage is defined as potential DIFFERENCE.

That's why voltmeters have two wires, to measure between two points.

In any circuit there is usually a point where all currents emanating from a power supply are collected for return to the power supply.
It is common practice to name that point "Ground" (though I much prefer "Circuit Common") and measure all circuit voltages with voltmeter's black wire connected there. We call that place where we put voltmeter's black wire "Reference", all voltages are said to be measured "Referred to" that point.
And it's handy to do that. Most but not all folks do so. It's very logical.

Observe that "Circuit Common" aka "ground" may have no connection at all to Earth ground. So even that nomenclature is confusing.
Earth is usually represented by a symbol resembling a garden rake.
MarcusAu314 said:
Could someone explain me please what does this GND stuff mean? I'm so confused. My confusion originates that in the fact that the circuit has a V+ and a - but what does the VGND have to do there?

As danenn said, somebody has created another "convenient" point to hook his voltmeter's black wire and named it VGND.
It is unfortunate that he chose the symbol for it that's usually reserved for circuit common or sometimes Earth ground, the three horizontal lines.

So in short,
GND is just another wire in the circuit.
It's the one chosen by the guy who drew the circuit as his preferred reference for all voltage measurements.
Nothing more.
Observe as in your example he may have several of them.

old jim
 
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  • #8
Everything the others said is true. But they didn't mention that it is called "ground" because that point is sometimes electrically connected to a conducting rod burried in the ground.

In houshold wiring, the physical connection to ground is handled by the house's wiring, so you need not be aware of it. But somewhere nearby GND and ground really do mean the same thing.
 
  • #9
anorlunda said:
they didn't mention that it is called "ground" because that point is sometimes electrically connected to a conducting rod burried in the ground.

Sometimes indeed. Often connected so , i concede.
But calling it "Earth" removes ambiguity. I prefer "Circuit Common" for circuits and "Earth" when connected to earthing conductors buried in the ground.

My 1956 Royal Enfield manual used "Earth" to mean cycle chassis even though it's insulated from Earth by the 'tyres'...
What price preciseness?

old jim
 
  • #10
So you basically mean that they mean the battery terminals?
 
  • #11
MarcusAu314 said:
So you basically mean that they mean the battery terminals?

Not quite sure what you mean there...
going back to your post #1
MarcusAu314 said:
I've been noticing that in some of them instead of being closed (in diagrams) they are like this.

trancurr-gif.80407.gif
Could someone explain me please what does this GND stuff mean? I'm so confused. My confusion originates that in the fact that the circuit has a V+ and a - but what does the VGND have to do there?

+9V and 0V would mean power supply connections, which could be terminals of a battery.
VGND i think we answered.
 
  • #12
MarcusAu314 said:
I'm a mechatronics engineering student, and I know that electronics is a requirement in most engineering programs. I'm been dealing with electronics recently and I've been studying electric circuits. I've been noticing that in some of them instead of being closed (in diagrams) they are like this.


My problem doesn't deal with the transistors, yet it deals that in some circuits I've found that they write something like in this case +9 V and 0 V. Also in some circuits I've found this:

Could someone explain me please what does this GND stuff mean? I'm so confused. My confusion originates that in the fact that the circuit has a V+ and a - but what does the VGND have to do there?

Thanks.
The 0 Volt or Virtual ground may be a stable noise free "active" ground that is isolated from any other kind of ground. It may be the positive supply terminal of the negative side of a dual regulated power supply for example. The Battery with the divider provides a dual output with capacitors to help stabilize the virtual ground. It could be the power source for the first circuit and the 0V could be the VGND.
 

Related to What does 0 V exactly mean in an electric circuit mean?

What does 0 V exactly mean in an electric circuit mean?

In an electric circuit, 0 V refers to the potential difference between two points. It means that there is no difference in electrical potential between the two points, and no current will flow between them. This can occur when the two points are at the same potential, or when they are connected by a short circuit or a wire with zero resistance.

Why is 0 V important in an electric circuit?

0 V is important in an electric circuit because it serves as a reference point for measuring potential difference. It allows us to compare the potential at different points in a circuit and determine the direction of current flow.

Can a circuit have 0 V at every point?

No, a circuit cannot have 0 V at every point. If this were the case, there would be no potential difference and no current would flow. In a closed circuit, there must be a difference in potential to drive the flow of electrons.

What causes 0 V in a circuit?

There are several potential causes of 0 V in a circuit. It could be due to a short circuit, where the two points in question are connected by a wire with zero resistance. It could also be due to a loss of power or a disconnected circuit component.

How can 0 V be measured in a circuit?

0 V can be measured in a circuit using a voltmeter. The voltmeter will have two leads that can be connected to different points in the circuit, and it will measure the potential difference between those points. If the reading is 0 V, it means there is no difference in potential.

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