grounded

[Ankit Gupta]

What is the meaning of earthing of any circuit ,I know its a child question . everybody says that it means 0 potential at that point but I didn't understand it till now I mean how current will be flowing after grounding in a circuit , what is the use of it in circuit other than 0 potential , how is circuit is completed after it ?

 

Please help me

[Enthalpy]

A non-trivial question.

 

Devices connected to the power grid can have their metallic housing connected to Earth. If some insulation malfunctions and a power line touches the housing, the Earth wire evacuates the current, so people don't get in contact with the line. In addition, "differential" circuit breakers feel that some current that goes in the device at one line doesn't come out at the other (as it flows through the Earth line), and this sign of malfunction lets the breaker go off. Law in many countries demand such an Earth connection, depending on varied conditions.

 

A lightning impact will find Earth whatever you do. Providing a good path to Earth means that the current there isn't destructive.

 

A connection to Earth avoids the accumulation of static charges.

 

----------

 

Then, in electronics... It gets more complicated, opinions vary among people and depend on each case.

 

A typical LW or MW wire antenna is single-ended; its current flows to an Earth contact. Both at the transmitter and the receiver.

 

Among various equipments, which ones should connect to Earth? It depends. Connecting them all is often a good beginning, but not with big currents and smal voltages at low frequencies, because then, the return currents flow in part through all Earth connections, and this lets the various ground potentials differ, so some people prefer to connect only one point to Earth. It's much a matter of personal experience.

[Ankit Gupta]

I didn't mean that I know that earthing of house hold appliances rather I wanted to ask the concept of earthing in small circuits like in a transistor

 

 

 

http://101science.com/images/transistor.gif

[Sensei]

What you have in gif circuit means that there is path/wire between bottom "grounding" and minus electrode on battery on top.

[Ankit Gupta]

OK leave it I think I'm not getting it how to explain what I want to know but i know i dont want to know what you r thinking

 

thanks for ur replies

OK leave it I think I'm not getting it how to explain what I want to know but i know i dont want to know what you r thinking .

 

thanks for ur replies

[Strange]

I didn't mean that I know that earthing of house hold appliances rather I wanted to ask the concept of earthing in small circuits like in a transistor

 

 

 

http://101science.com/images/transistor.gif

 

It is just a symbol to show where the (arbitrary) zero volt reference is in the circuit. It doesn't mean this point is grounded. It just means that point is to be considered as 0V; voltages above that are positive and voltages below it are negative.

[Ankit Gupta]

It is just a symbol to show where the (arbitrary) zero volt reference is in the circuit. It doesn't mean this point is grounded. It just means that point is to be considered as 0V; voltages above that are positive and voltages below it are negative.

would u please explain it further like where it is positive and where to take negative by showing it in a circuit

 

 

and thanks to u for understanding what I want to ask .

[Strange]

would u please explain it further like where it is positive and where to take negative by showing it in a circuit

 

Imagine you have circuit powered by a 6V battery, for example. You can mark the negative terminal as 'ground' and then the other terminal will be +6V. Or you can mark the positive terminal as ground and then the other terminal will be -6V.

[studiot]

An earth (british english) or ground (american english) is a circuit element.

 

The idealisation only exists in theory, but the planet Earth can come pretty close for some purposes.

 

Most circuit elements have at least two terminals also called nodes.

For example a resistor has two, a transistor has three external terminals.

 

An earth has only one terminal.

 

Its properties are such that however much current (or charge) passes into or out of the earth, the potential of the earth node does not change.

 

This potential may not be actually zero, but we usually find it convenient to call it so. This is like using sea level as a zero for elevation. sea level is not actually at zero distance above the centre of the earth but we call it zero and reckon elevations above sea level as positive and depressions or depths below sea level as negative..

 

This propertiy of maintaining itself at a fixed voltage has three main uses.

 

Firstly as a protective earth, as in house wiring.

 

Secondly since the voltage never varies there can be no electromagnetic radiation (radio waves) propagating in an earth. So it is used for screening and shielding.

 

Thirdly for your purpose we can use it as a voltage reference point for the rest of the circuit since, no matter what happens in the circuit, its potential does not change. Any other point in the circuit is liable to undergo change of voltage due to circuit action whether wanted or unwanted. In this respect, 'earths' are better than sea level because there is no equivalent phenomenon to tides in electricity.

Edited December 28, 2013 by studiot

[MigL]

As others have explained, it provides a common ( sometimes also used ) reference for signals and potentials, such that they are measured from the same point, ie. ground potential.

[studiot]

 

As others have explained, it provides a common ( sometimes also used ) reference for signals and potentials, such that they are measured from the same point, ie. ground potential.

 

 

It's more than that. A reference point is no use unless it can be relied upon not to change when other things do.

[Strange]

 

It's more than that. A reference point is no use unless it can be relied upon not to change when other things do.

 

That is largely a matter of designing with suitably low supply line resistance, appropriate power supply noise filtering, etc.

[studiot]

 

suitably low supply line resistance,

 

Be careful of associating an earth with low resistance (or impedance). This is not always the case.

 

For example what is the resistance of the granite underlying New York?

 

Secondly, earths are (or should be) designed to carry no (zero) current in normal circuit operation.

Edited December 29, 2013 by studiot

[Strange]

 

Be careful of associating an earth with low resistance (or impedance).

 

I was more talking about the zero volt supply in an electronic circuit (which, despite being shown with a 'ground' symbol, is often not attached to ground/earth at all).

[studiot]

My PP3 battery does not have a terminal marked zero.

 

It only has terminals marked + and -

 

I think it is important to be clear and precise about statements as many learners take forward incorrect or partially correct ideas as a result of loose talk.

 

[Strange]

My PP3 battery does not have a terminal marked zero.

 

It only has terminals marked + and -

 

I think it is important to be clear and precise about statements as many learners take forward incorrect or partially correct ideas as a result of loose talk.

 

 

That is the point I was making in post 8. I suppose electrical engineers are worried about an absolute zero reference, that is connected to ground/earth. But in electronics, we usually don't care; it is just an arbitrary reference. My circuit only depends on the difference between Vdd and Vss - it doesn't matter if Vss is 0V or 200V.

 

p.s. just looked at the OP again: it isn't clear if he is referring to electrical or electronic circuits. I assumed the latter as that is my background.

Edited December 29, 2013 by Strange

[studiot]

The op actually specifies better in post#3

 

 

However there are many pitfalls in referring to zero volts as earth.

 

Take for instance an integrated (HiFi ?)amplifier.

 

It will have zero volts rails for the preamplifier and zero volts rails for the power amplifier.

It may also have separate + and - supply rails.

It may have red and black speaker terminals.

It may have a terminal on the case marked Earth.

These may all be on the same circuit board, as in the Marshall 8000 series.

If multichannel it may repeat some or all of these for each channel.

 

Which one of these (if any) can be considered as earth?

 

Which one do you connect the screen earth of a connecting cable to?

What if that cable is an blanaced or XLR connector?

 

How do you avoid earth loops with this amplifier?

 

I think you will find that you will find that you need all of my post#9 to properly answer these questions and wire this amp up correctly.

 

Another feature of some circuits is an earth or ground plane.

 

I think the OP is reasonably asking for guidance that will carry him into the future and that there are many variations that come to light when you delve deeply into the subject.

Edited December 29, 2013 by studiot

[Ankit Gupta]

Till now I didn't studied the electronic s too much and I know only few of it therefore I didn't understand many of ur terms so please would u explain it in a simple language to me so that I can make my self to understand more of it

[Strange]

Till now I didn't studied the electronic s too much and I know only few of it therefore I didn't understand many of ur terms so please would u explain it in a simple language to me so that I can make my self to understand more of it

 

I think you will have to say which terms you do not understand, then we can try and explain better...

[Enthalpy]

Is the difference between the English ground and earth only a matter of US versus UK? In other languages it's a physical distinction.

[Ankit Gupta]

Whole 16 and 17 post

[Strange]

I will explain post 16 a bit, as it was mine.

 

In an integrated circuit (where most of my experience is) there are typically two power supply lines called Vdd and Vss (for historical reasons). You can think of these as being connected to the two terminals of a battery. Vss is normally considered to be 0 volts. When I started out, Vdd was typically 5 volts. (Over time as transistors have got smaller, Vdd has dropped to 3.3V then 1.6V and 1.2V ... I don't know where it is now... And there my be several different Vdd and Vss suplies in complex circuits.)

 

The only important thing in the circuit is the difference between Vss and Vdd. Because Vss is considered to be 0V it may be shown with a ground/earth symbol. In reality, it may not be connected to ground at all. If the electronics is controlling some high-voltage equipment, it might be that Vss is 200V and Vdd is 205V.

 

But, as studiot says, there are cases where the ground is important as a shared reference between different pieces of equipment.

 

And for power distribution, it can be vital because you need to know that the exposed metal parts of equipment are safe (i.e. connected to ground) so you don't get a shock.

 

Hope that helps.

[Enthalpy]

Law does not demand that exposed metal parts of an equipment are grounded.

[Strange]

Law does not demand that exposed metal parts of an equipment are grounded.

 

I assume you mean "law" in a legal sense? (Rather than a physical law, for example.)

 

In which case, it depends where you are. In Europe electrical equipment must be either grounded or "double insulated". I don't know about other jurisdictions. I'm sure there are some where there are no regulations at all.