Power supply ground and battery ground

[electronicslearner77]

Hi all,

I have this clarification, if you use any table power supply the ground of it is connected to the earth through the plug point, so the return path is to the earth and hence it acheives 0V (am I correct in this?). But, when I use a battery the negative of a battery is not grounded then how does it get 0V? I am little bit confused in this. Could someone please explain me this?

Thanks and regards,
Satya

 

[Nigel Goodwin]

All measurements are relative - you measure from a reference point to the measurement point. It has nothing to do with ground at all.

For a battery operated item you would usually use the negative of the battery as the reference, but you could just as easily use the positive (then all readings would be negative). If it was a split supply design (such as for an opamp), you would normally use the split point for the reference, and have both negative and positive voltages.

 

[electronicslearner77]

Let us say the battery is 12V, then should I think this 12V is because
negative is 0V and Positive 12V or
negative is 1V and Positive 13V etc
or I should not bother about this? or I should always be thinking what is the difference between Positive and Negative?

Thanks in advance,
Regards,
Satya

 

[KeepItSimpleStupid]

(1) Not all table supplies are grounded. The terms are isolated and non-isolated supplies. Your laptop power brick is probably isolated, but it may contain a mains ground for RFI elimination. A table model supply may contain a ground point, which you can use or not. Not all are grounded.


As was stated previously, voltages are relative. Suppose I had a 12 V battery and hooked up a "rail splitter" IC to one. A rail splitter makes an "artificial reference" at 1/2 the battery voltage.

Now, let's suppose I designed a circuit using a dual-supply OP-Amp. The reference (0V) is going to be 1/2 the battery supply for the input and output signal. When I measure the battery, the neg terminal would be an appropriate 0V reference.

Voltages are relative. Earth ground is convenient and so is battery ground, but not always appropriate for the measurement.

 

[ronsimpson]

Even earth ground is relative. The earth is about a million volts away from the sun's voltage.

 

[KeepItSimpleStupid]

And then there is the issue that the Earth's ground isn't even a constant especially during thunderstorms.

 

[Willen]

So then can I make a power house and produce electricity pluging tow terminals 1st from the sun for positive and 2nd fromThe earth for negative? (theotically) OR between Earth and moon?

 

[KeepItSimpleStupid]

And just remember, that to avoid the suns intense rays, go at night.

 

[ronsimpson]

So then can I make a power house and produce electricity pluging tow terminals 1st from the sun for positive and 2nd fromThe earth for negative? (theotically) OR between Earth and moon?

Yes but there will be some copper loss. Could use gold wires.

And just remember, that to avoid the suns intense rays, go at night.

Night.....shoot, I did not think about the sun going away at night.
OK I got it. It takes 8 minutes (approx) for electricity to go from the sun to earth. If the wires take a very indirect rout we could get a 12 hour delay. Electricity at night!
OR
We could build a really big capacitor to store the electricity from the sun until we need it. Should work as long as the cap does not roll off the edge of the earth.

 

[aljamri]

Let us say the battery is 12V, then should I think this 12V is because
negative is 0V and Positive 12V or
negative is 1V and Positive 13V etc
or I should not bother about this? or I should always be thinking what is the difference between Positive and Negative?

Thanks in advance,
Regards,
Satya

So that it is called some times "Potential Difference".