Single terminal of battery alone connected to earth.

I took a 12 Volt battery and connected its positive terminal to one end of LED bulb with enough series protection resistor. Then i connected the other end of the LED bulb to earth (soil with moisture outside my house). I did not connect negative terminal of the battery to anything. I expected the bulb to glow. But it did not glow until i connect the negative terminal also to ground. While there is potential difference between earth and battery why dont current flow through bulb when i did not connect negative terminal to earth.

 I have attached the photo of the battery that i used.
 I am sure that LED's were working properly and battery had enough capacity to provide current.

Comments

[gmoon]

"Ground" is generally a misunderstood term.

The difference in electrical potential exists between the positive and negative terminals of your battery. There is no inherent relationship between the (-) terminal of a power supply and "ground." Don't confuse the two. Connecting to (or labeling) the negative as such is merely the most common usage of ground.

Ground is simply a reference. It's perfectly acceptable to connect the positive battery terminal to ground. Connected in such a way, positive is the ground reference and the negative terminal of your battery is now -12 volts when compared to ground. But there is no difference in the potential between the two battery terminals.

Bipolar power supplies have the ground reference in the middle, between a positive and a negative supply (like +/-12V).

At one point early in the transistor revolution it was quite common that circuits built around PNP transistors had a positive ground. Most computer power supplies are bipolar, or include a negative voltage component.

[kelseymh]

Because without connecting the negative terminal of the battery, you had an open circuit. If you don't know what "open circuit" means, please visit your local information resource facility and find out. We aren't here to do your homework for you.

[deepakmurali]

Try to learn how to communicate with people from Frollard.

[frollard]

http://www.youtube.com/watch?v=rg-XFXdtZnQ
^will probably be taken off youtube soon for copyright infringment; but its the electricity episode.


From about 2 minutes onward you see why a circuit is important.

[iceng]

Nice 1993 Vid, I met Bill Nye that scientific guy in New Orleans years ago.
Thanks for posting it :-)

[frollard]

He is my hero. My goal is to meet him before either of us kicks the bucket!

[frollard]

**while there is a potential difference between the terminals on the battery, there is no potential difference between just one of the terminals and some other arbitrary object like 'ground'. That would be static electricity. in order to have AC or DC it really wants a circuit. (***most*** of the time)

[deepakmurali]

Thank you for replying properly.

If that is so then what about this case? I will connect positive terminal of 12 v battery to ground (negative terminal will not be connected) and then positive terminal of 6 volt battery to the ground and in this case also i wont connect negative terminal of the battery. While there is potential difference of 6 v between both positive terminals of battery, will it be like there is no potential difference between one terminal of each battery and earth?

It is like saying a=b=a, but a is not equal to c.

Please help me

[frollard]

Again, without a circuit, there is no potential difference.

Batteries in a very rudimentary form act as an electron pump, it needs an input and an output -- otherwise it does no work.

if you had

{not connected)---A---battery++++ ground ++++battery---B----(not connected) between

assuming ground is conductive in this case
testing between A and B you would have a circuit (through the tester) and since the batteries are parallel (positive to positive) would be battery1 minus battery2 voltage (which they generally don't like).