Position of unknown material on electrostatic series?

[LegitSci]

Homework Statement

You have a new unknown material. You want to get a rough approximation as to the location of the unknown material on the electrostatic series. You only have two tools at your disposal; some wax and a charge detector. Design an experiment (procedure) that will help you infer whether the unknown material is near the top of the electrostatic series (above wax) in the middle of the electrostatic series (near wax) or at the bottom of the electrostatic series (below wax).

Homework Equations

I don't think there are any relevant equations.

The Attempt at a Solution

I have no idea of how to find the TYPE of charge. I am thinking that the only way to solve this is if the charge detector has a known charge itself and I could separately compare their respective charges after the rubbing them together. Since the charge detector does not have a known charge, the only useful information it could give is IF the material has a charge. Or can charge detectors (e.g. electroscopes) measure polarity as well?

 

[andrevdh]

Yes. They can. If you charge it with a known charge and
you bring a similarly charged object nearby they deflect more.
If you bring and uncharged or oppositely charged object
nearby they deflect less. Maybe you can charge the
object by rubbing it with your hand? List some of the
materials in the series here so that we can see it.
Wax on wax might also give you a definite charge,
which I can only guess at.
http://www.sciences.univ-nantes.fr/sites/michel_maussion/statelec/index.html

 

[LegitSci]

I know that charge detectors can identify polarity, IF itself has a known charge. The only problem is that I am only allowed to the mystery material, wax and a charge detector. I guess that rules out hands. By listing, do you mean the whole electrostatic series? Because this problem is relative to only wax and mystery material, and not much information is given which would hint to a definite material on the electrostatic series. Also I don't think that rubbing wax on wax will do anything because to create static electricity, each material should either have a deficit or excess amount of a charge (positive/negative). Wax on wax would just neutralize each other, I would think.

Thanks for your input!

 

[andrevdh]

Lets assume the two materials are near each other on the electrostatic
series (ES), or also called the triboelectric series.
How could you use the charge detector (CD) to determine this?

 

[LegitSci]

Well, if the charge detector has a known charge, I could test and compare the magnitude of the attraction/repulsion between the mystery material and wax. If there was a greater force (attraction/repulsion) then the mystery material would be farther away from wax in either direction (depending on the charge of the charge detector and the respective materials)

Correct me if I am wrong.

Thanks

 

[andrevdh]

The electrostatic series is constructed so that if a material below it
on the series is used to charge it up the material below it on the
series will remove electrons from it, that is it will be charged positively
and the further down in the series it is the more electrons it will remove.

And yes, i do agree with you that in order to identify the charge the
detector needs to be charged with a known charge. The only way
I can think of this can be done is to charge the wax up with your
hand, which would render it negatively charged. The detector only
shows if and by how much the material is charged.
http://faraday.physics.uiowa.edu/em/5A10.15.htm
Notice that human skin is listed at the top in one of the series (right at the bottom).
There might be another way of identifying the charge on a body without using other
equipment - I might look into it...

 

[LegitSci]

Unfortunately, I don't think I am allowed to use hands...
Do you think maybe the answer lies in the TYPE of charge detector?
Are there any detectors that are maybe able to determine the polarity of a given charge without itself having a known charge?

Thanks

 

[andrevdh]

Yes, you do get such - see this interesting one by Tomas Kim
but I can't see how you are going to do the investigation without using your hands (joke)!

 

[LegitSci]

Haha funny!
Thanks for the info about the charge detector. Does it still fall into the scope of an electroscope?
Or do electroscopes only detect IF there is a charge?

 

[andrevdh]

There are many types of electroscopes. Some indicate only if the object is charged and others also the degree to which it is electrified. This one indicates if the object is charged and what type of charge is present. So one could classify it as an electroscope too.