Can an electrostatic force repel or just attract?

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Discussion Overview

The discussion centers around the nature of electrostatic forces, specifically whether charged plates can repel each other or only attract. Participants explore various scenarios involving charged plates, grounding, and the effects of potential differences, touching on both theoretical and experimental aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants assert that two charged plates can repel each other if they have like charges, while others argue that grounding one plate leads to attraction due to induced charges.
  • One participant expresses confusion about the conditions under which repulsion occurs, questioning the scenarios that would lead to such an effect.
  • Another participant explains that a negatively charged plate induces a positive charge on a grounded plate, resulting in attraction, while a positively charged plate induces a negative charge on the grounded plate, also leading to attraction.
  • Several participants discuss practical experimentation, with one noting that they were unable to observe repulsion when attempting to charge two plates with the same polarity.
  • There are suggestions that the forces involved may be too small to measure easily, and one participant encourages calculations to understand the forces better.
  • One participant describes methods to compare attraction and repulsion, including disconnecting voltage sources and observing the behavior of charged plates.
  • A later post introduces a new topic regarding the potential for negatively charging a space suit to mitigate issues with positively charged moon dust, raising questions about the feasibility of creating a "wall" of electrons as a protective measure.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether electrostatic forces can lead to repulsion under specific conditions, with multiple competing views and ongoing confusion about the scenarios that allow for repulsion.

Contextual Notes

Some participants express uncertainty about their experimental setups and calculations, indicating potential limitations in their understanding of the electrostatic principles involved.

Who May Find This Useful

This discussion may be of interest to individuals exploring electrostatics, experimental physics, or those involved in practical applications related to charged materials and their interactions.

ak_47_boy
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[SOLVED] Can an electrostatic force repel or just attract?

Two charged plates can't be made to repel each other right?
 
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ak_47_boy said:
Two charged plates can't be made to repel each other right?

Yes they can, just not on the same potential ofcourse

marlon
 
So, a positively charged plate will be attracted to a grounded plate and a negatively charged plate will be repelled by a grounded plate.

Sorry if i make no sense, i have myself confused.

Edit: This makes no sense because as long as there is potential difference between the plates they will attract each other. What scenario would cause repulsion?
 
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No. A ground plate is inherently at 0V. It is connected to Earth which by definition in electronic engineering (and perhaps physics) a source of infinite charge, both positive and negative.

A negatively charged plate will induce a positive charge on an earthed plate and they will attract. A positively charged plate will induce a negative charge on the earthed plate and also attract. It is only if you get like with like...so two positively charged or two negatively charged.
 
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How would i make two plates repel each other then? I tried hooking the positive of a 15kv hene ballast to two plates and nothing happened. This would work if i had two separate supply's correct?
 
It's probably because the force that the places exert on each other is too small to be easily observed or measured. Have you tried to calculate it?
 
ak_47_boy said:
Two charged plates can't be made to repel each other right?
Yes. Since like charges repel and unlike charges attract all you have to do is simply place charge of one sign on one plage and charge of the opposite on the other plate.

Best wishes

Pete
 
jtbell said:
It's probably because the force that the places exert on each other is too small to be easily observed or measured. Have you tried to calculate it?

The plates snap together with 15kv between them, i would think should be able to repel each other with the same force? I have tried calculating it but i don't know if what i am calculating is correct.

pmb_phy said:
Yes. Since like charges repel and unlike charges attract all you have to do is simply place charge of one sign on one plage and charge of the opposite on the other plate.
Pete

Yes, i have done that and it worked very well. But how do you make them repel each other.
 
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Perhaps there is some flaw in your experimentation? I am not familiar with a 15kV hene ballast. When you perform the experiment with the plate charges equal and opposite to one another how do you connect the equipment?

How do you connect it in the experiment to charge the plates with like charges?
 
  • #10
To make them attract i simply hook the positive to one plate and the negative to the other. In an effort to try to make them repel i hooked the positive to both plates while grounding the negative, and nothing happened.
 
  • #11
You seem to have a lot of confusion here. Go back to something simpler. Have you ever played with an electroscope before? Try to figure out the nature of the charge induced in there.

Zz.
 
  • #12
ak_47_boy said:
So, a positively charged plate will be attracted to a grounded plate and a negatively charged plate will be repelled by a grounded plate.

Sorry if i make no sense, i have myself confused.

Edit: This makes no sense because as long as there is potential difference between the plates they will attract each other. What scenario would cause repulsion?

hi ak_47_boy i am ricardo19 an aswer to your question

different polarities atract and equal polarities repel
follow this example am sending you, and tell me if it was good for you
 
  • #13
Ricardo19 said:
hi ak_47_boy i am ricardo19 an aswer to your question

different polarities atract and equal polarities repel
follow this example am sending you, and tell me if it was good for you

http://www.gcsescience.com/Attract-Repel-Electrostatic-Charges.gif
 
Last edited by a moderator:
  • #14
The reason that the plates with opposite charges attract so much more than like charged plates repel, if you put the same voltage on them Is that there is much more charge on them. Because the opposite charges attract each other more charge is drawn into the plates. If you put the same charge on the plates this will oppose the buildup of charge.

If you want to compare repulsion and attraction there are two ways:

1 charge the opposite charged plates when they are far away from each other, then disconnect the voltage source and bring them together. you should see the same
repelling force as you previously did.

2 use two sets of plates that you give opposite charges. Disconnect the voltage source and then bring two plates with the same charge together.

If you pull apart a charged capacitor, the voltage will go up.this could lead to leakage, sparks AND BE DANGEROUS IF YOUR CAPACITOR WAS BIGGER THAN 1nF.
I have seen this experiment done. you need to cover the edges of the plates with a good insulator and put some grips on them made of an isolator. Do not put the plates near anything that isn't a good insulator (such as yourself)
If you use 100 cm^2 plates with 1 cm initial distance there isn't any danger, but your charge might easily leak away if you're not careful.
 
  • #15
Ok, I have it working just as you described.

Thanks!
 
  • #16


I have this project on moon colonisation. when i was researching i came across moon dust aka regolith. this substance has a net positive charge. i thought that some how negatively charging a space suit would solve this problem. is this possible? any other ideas?

Also is it possible to crate a "wall" of electrons or negative electroststic charge, like a shield, around a person?
 

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