Drawing electric charge from the earth

  • Thread starter kunalkb20
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  • #1
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I recently learned about r-c circuits and was wonderring that if earth can provide electrons then why is it not used as a source of charge?
Will the below circuit be successful in drawing charge?

................................................... __________ (Isolated Positively Charged Plate)
................................................... + + + + + +
.................................................... __________ (Neutral Plate)
.............................................................|
.............................................................|
Please ignore these dots............................<
They are only meant to maintain indenting.......>
............................................................< (Resistor)
..............................................................>
..............................................................l
....................................................______|______
........................................................________
............................................................____ (Earth)
.............................................................._

What might happen here is that since the neutral plate is grounded, it will draw charge from the earth to make its potential zero.
As the charge is drawn, it will be utilised by resistor so theorotically the plate will take infinite time to get charged.
As the capacitor gets charged, the current will reduce. However, when that happens, the earthed plate can be neutralised again to regain stronger flow of current and the process restarted.

Will this circuit practically work?
 

Answers and Replies

  • #2
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What might happen here is that since the neutral plate is grounded, it will draw charge from the earth to make its potential zero.
As the charge is drawn, it will be utilised by resistor so theorotically the plate will take infinite time to get charged.
As the capacitor gets charged, the current will reduce. However, when that happens, the earthed plate can be neutralised again to regain stronger flow of current and the process restarted.

Will this circuit practically work?

Why it will draw charge from earth? already the the capacitor and resistor are at zero potential. There is no closed path in the circuit and hence the capacitor cannot get charged.
The law of conservation of energy has to be kept in mind. Work has to be done to charge a capacitor. Where does this work come from in your circuit?
 
  • #3
5,441
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Well I think the 'neutral' plate will become negatively charged by elctrostatic induction.

But a question for the OP

How would you 'neutralise' this plate again?
 
  • #4
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Karthick,
If you observe the circuitry, you will see that only ONE plate and not the entire capacitor is grounded. So the potential of the grounded plate and not the entire capacitor must be zero and in order to do that, negative charge must be pulled from the earth to neutralise the effect of the positively charged plate. Also, the work is being done by the electrostatic force exerted by positive charges.

Studiot,
I agree that the neutral plate will become negatively charged over time but when that happens, it can simply be disconnected, taken far enough from the positive plate and grounded so that the negative charge flows back to the earth. This will make it neutral again.
 
  • #5
2,044
312
Studiot,
I agree that the neutral plate will become negatively charged over time but when that happens, it can simply be disconnected, taken far enough from the positive plate and grounded so that the negative charge flows back to the earth. This will make it neutral again.

It does take energy to pull the plates apart, since one of them is positively charged,
and the other one is negatively charged.
If you leave the plate that is grounded back and forth, you get an alternating current through the resistor, and this is how a capacitor microphone works, but you just convert mechanical energy into electrical energy.
 
  • #6
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Okay but the capacitor will only be fully charged at t=infinite. Does that mean that charge can continuously be drawn from the earth till the current becomes too little to be able to use?
 
  • #7
5,441
9
I'm not quite sure what your aim is here.

There is a ban on 'free energy' and 'perpetual motion' discussions at PF.

Remember that you have to somehow charge the positive plate in the first place.
 
  • #8
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I am sorry if i am bending rules here but i really thought that this could prove to be an efficient source of electricity.
As for the plate to be charged, two plates can be connected to either terminals of the battery, charged and the positive plate removed and used. The next question would be that if a battery exists then what is the need of undergoing so many processes. Well the whole point of this experiment is that all one needs to do is charge the plate once and with that one charged plate, charge can be drawn from the plate n number of times.
 
  • #9
5,441
9
You misunderstand the difference between potential and charge.

You do not 'charge a plate' by connecting it to one terminal of a battery.

Whilst the plate is connected it has the same potential as the terminal, but the amount of charge to achieve this is negligable.

Once you remove the battery the charges redistribute and the plate is again neutral, ie at an indeterminate potential that would read zero on an avarage reading voltmeter.

So I'm sorry to disillusion you but your scheme won't work and conservation of energy (which by the way is the product of charge and potential) is preserved.

go well
 
  • #10
sophiecentaur
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Congrats on the graphics. It took me back to the teleprinter days!:smile:

Studiot's mention of electrostatic induction made me think of the Electrophorus and similar equipment. All these methods of moving charge from place to place involve mechanical work being put into the system Once charges have flowed to establish equilibrium then that's your lot - until you do some more moving about, using energy input.
 
  • #11
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Thank you sophiecentaur :) Couldnt find a better way to depict what i was thinking.
I had this on my mind for quite a while.
Thanks a lot studiot for explaining the topic.
 
  • #12
5,441
9
What you have proposed has a grain of truth in it.

Unfortunately it is not free energy.

Every year in the UK a handful of farmers are prosecuted for stealing electricity by a variation of your method.
They have discovered that if they lay a line in the ground directly under a high voltage national grid cable passing over their field they can extract significant power from the voltage induced in the buried line.

This is not free, as they think, but can be and is detected as a power drop at the line monitoring station. The investigation of this loss soon reveals the culprit who then has to face justice.

There is no such thing as a free lunch in this universe.
 
  • #13
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But how does the line monitoring station detect the power drop? If the line is buried independently then how does it affect the high voltage grid cable?
 
  • #14
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I think I've said enough.

go well
 
  • #15
sophiecentaur
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But how does the line monitoring station detect the power drop? If the line is buried independently then how does it affect the high voltage grid cable?

For a start, all they need to do is to look at your bills and compare them over a period of time. If there is a sudden appreciable drop in apparent consumption then they will smell a rat. Once you are suspected, then they can compare your meter reading with the reading at a meter, placed temporarily upstream of your property.

I wouldn't mind betting that it frequently goes on, undetected - as long as the thief is not too greedy (as with many crimes).
 
  • #16
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Smart. On both their parts actually, but i think i would prefer paying rather than getting stuck in a prison cell :) ! Anyway, thank you Sophiecentaur and Studiot.
 
  • #17
Drakkith
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Now, I'm assuming the amount of work needed to physically move the negatively charged plate would be greater than what you would get out of the built up charge? And connecting a cable to the negative plate wouldn't do any good because the positive plate is attracting all those charges still, so no way to get at them.
 
  • #18
QuantumPion
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But how does the line monitoring station detect the power drop? If the line is buried independently then how does it affect the high voltage grid cable?

I think they could detect the inductive load on a single phase of the transmission line. However after googling around I found http://www.physics.unc.edu/~deardorf/phys25/rwp/exam1rwpsolution.html" which demonstrated the infeasibility of stealing power this way.
 
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