Static Electricity and dc motor

[Flynxi]

If take a simple dc motor and connect the negative side to let's say a insulated metal plate. The other side directly to ground and you then turn the shaft of the motor. Would you force all of the free (loosely using all) electrons in the insulated metal plate through the motor to ground giving the metal plate a net positive charge? If then while the system is running you removed the connecting wire between the motor and the insulated metal plate would it (the insulated metal plate) keep the net positive charge?

Thank you for taking the time to read my question. This is not for any school work and is just a personal inquiry as I am unable to find an answer on google for any search query I am able to think of.

 

[phinds]

I am unable to find an answer on google

Even though it's not homework, how about trying to SOLVE the problem instead of looking to be spoon-fed the answer by getting it here or from Google?

 

[Flynxi]

Even though it's not homework, how about trying to SOLVE the problem instead of looking to be spoon-fed the answer by getting it here or from Google?

Hello, I am sorry that I have come across as trying to be "spoon-fed". I only have a high school education and have been trying to see if I could find a answer on this for a couple weeks now before I had posted here. By solve do you mean setup an experiment and test? If so I can definitely do that but I don't have anything so I would have to buy the things to try such is why I am asking first. But also how would you measure if a object had a net positive charge, a voltmeter? Again I am sorry if I made the impression that I would like to be spoon-fed a answer and I don't wish to make it seem that way.

 

[phinds]

Hello, I am sorry that I have come across as trying to be "spoon-fed".

Fair enough. I may have gotten carried away by the general PF point of view which is that we are help to help people learn how to sovle problems as opposed to being here just to give answers.

I only have a high school education and have been trying to see if I could find a answer on this for a couple weeks now before I had posted here. By solve do you mean setup an experiment and test?

No, I was not suggesting an experiment, but logic.

 

[davenn]

I must add I hope Phinds response doesn't deter anyone from answering this question. I saw much simpler questions asked that didn't get this type of response that are a google search away and thus is why I decided to ask, I didn't expect to get such a response.

all good, no problems
At PF, we help people help themselves

How would I go about testing if a object has a net positive charge if I did this?

for a start, draw a circuit of your setup and then consider what you know about basic circuits and what is required for a current to flow

post your drawing and response Dave

 

[Flynxi]

Fair enough. I may have gotten carried away by the general PF point of view which is that we are help to help people learn how to sovle problems as opposed to being here just to give answers.

No, I was not suggesting an experiment, but logic.

Thank you for responding, and again I don't wish to give the wrong idea. My logical thinking would tell me it wouldn't work because you would need a full circuit to make it work, but then again I couldn't find anything describing this especially if you were to somehow use a DC motor that could generate a very high voltage.

 

[davenn]

My logical thinking would tell me it wouldn't work because you would need a full circuit to make it work,

that's good

but then again I couldn't find anything describing this especially if you were to somehow use a DC motor that could generate a very high voltage.

replace the motor with a battery, do you think there will be any difference ?

 

[Flynxi]

that's good
replace the motor with a battery, do you think there will be any difference ?

Well if you used a high enough voltage my intuition would tell me that it would ionize the gas around the metal plate? Because if you did hook up such a circuit and tested the voltage from the metal plate to ground there would be a voltage difference correct? So I would think this would create a kind of static charge in the object. If the voltage was high enough it would bring electrons in from surrounding gas.

I think of this because of how clouds in lightning work. It ionizes the gas to pull electrons from ground because the positive charge is great enough. If the voltage was enormous enough wouldn't it do the same thing and pull electrons from ground to complete the circuit?

 

[davenn]

Well if you used a high enough voltage my intuition would tell me that it would ionize the gas around the metal plate?

that's going to take 10's or 100's of 1000's of volts and isn't going to happen with a battery or motor so let's no go there
so let's be realistic and say a motor and a battery that can produce 100V and keep it closer to your original scenario

I think of this because of how clouds in lightning work. It ionizes the gas to pull electrons from ground because the positive charge is great enough.

not quite how it works ...

generally the base of the cloud is negatively charged ( to can be the other way on occasions) and the ground is positively charged.
This produces a huge electric field between the cloud and the ground over quite a distance up to 1km or so because of the millions
of volts of potential difference that is generated. That electric field causes the air in between the ground and the cloud base to start
to break down ( no ionisation has occurred yet) and there are "fingers" that start reaching down towards the ground that finally meet
up with one coming up from the ground. When they meet, the discharge occurs and we see the flash and at the same time there is
strong ionisation along the lightning channel

here's a video of all those "fingers" reaching out from the cloud base

https://www.bing.com/videos/search?...31CFCB844E4964BD3DDC31CFCB844E496&FORM=WRVORCDave

 

[Mister T]

Because if you did hook up such a circuit and tested the voltage from the metal plate to ground there would be a voltage difference correct?

How does it come about that the negative electrode of a battery has a negative charge and the positive electrode has a positive charge?

 

[Vigant]

When experimenting with static electricity a high voltage is usualy used.
But of course the principle functions at low voltage as well.

Your insulated plate and ground makes together a capacitor.
So if you ground the plus pole of a battery and connect the minus pole to the plate for a moment then the plate will indeed have a negative potencial against the ground (as the capacitor got charged).

The only problem is that the negative charge on the plate is so week that it can be hardly detected with something.
This is because the capacitance of the plate is very small and so is the voltage.

 

[Flynxi]

Thanks dave for clearing that up for me.

that's going to take 10's or 100's of 1000's of volts and isn't going to happen with a battery or motor so let's no go there
so let's be realistic and say a motor and a battery that can produce 100V and keep it closer to your original scenario
Dave

How does it come about that the negative electrode of a battery has a negative charge and the positive electrode has a positive charge?

The only problem is that the negative charge on the plate is so week that it can be hardly detected with something.
This is because the capacity of the plate is very small and so is the voltage.

Since 100KV capacitors exist couldn't you use something of the sort. Charge the capacitor then switch to to the system I was speaking of would cause a large voltage potential, so theoretically if you had millions of volts this would happen? And based on my reading this would make a "virtual electrode" that is extremely negatively charged (in relation to the plate) surrounding the plate since the plate would have such a positive potential comparative to the surrounding gas, or am I not thinking about that correctly?

Edit: Couldn't you use something like a Van de Graaff generator or Cockcroft–Walton generator to create the voltage difference of millions of volts DC (Relatively) pretty easily?

Edit, Edit: I just really wanted to thank all of you for taking your time and explaining these things for me and conversing with me. This is really great fun and thank you all again! :)

 

[sophiecentaur]

I am unable to find an answer on google

You have my sympathy here (the first time you have approached PF in this way) and learning to search for 'the answer' is a skill that we all need to acquire. It is unlikely that you will ever find an answer that is specific to a question like yours so you must be prepared to find your way through. It will also require you to read a lot of the links you come up with and not to reject a link just because it doesn't contain a word that's in your particular question. If you are prepared to go through 'academic based' websites like Hyperphysics and take on board the basic Physics then you are more likely to be able to re-formulate your initial question so that it will actually produce an answer.
Unfortunately, the availability of PF and other sites encourages the Q and A method of getting knowledge. It really is a pretty hopeless way to advance an appreciation of a subject like Physics.
In the simple case in the OP, the motor will be producing a potential difference across it as it is rotated. (It would be easier to consider a simple battery instead of the motor (used as a generator, actually) - exactly the same situation in principle. How many electrons (or what actual Charge)will be displaced (formula Q = CV and you can assume a capacitance of perhaps 50pF)? What voltage would your generator / battery need to displace an electron from each atom in the motor or plate? (A mind blowing number)
So you will have charged up the metal plate. If it is then removed from the + terminal, is there any path by which electrons can flow onto or off the plate? So how could its charge alter?
There will have been hundreds of links from Google which would have told you that - as long as you had grasped what your 'motor' scenario has in common with those examples which the sites will all describe. Be prepared for answers that may not always apply to your initial question. Look for the common ground.