Returning electrons without copper wire?

Thread Starter

Silhorn L

Joined May 2, 2017
7
Hello,

I have a question about the wool and the wax on this page.

https://www.allaboutcircuits.com/textbook/direct-current/chpt-1/voltage-current/

If we rub the wool and the wax then there will be a surplus of electrons in the wax.

If we separate the 2 materials and then make them on contact again will the electrons be returned to the wool?

It seems to me like it should because their is difference in potential between the 2 materials but it looks like it will only do that if you connect a copper wire to both materials?
 

oz93666

Joined Sep 7, 2010
737
The wool and wax are separate , and have a voltage difference , as they are brought closer together the voltage may be great enough for a small spark to jump ... suppose the voltage difference was 2KV at about 2mm a spark will occur and the two should be at the same potential..

Either way by the time they touch they should be at the same potential ... the copper wire just allows discharge at a great distance.

This brinks up the question if contact allows discharge , how was it possible for them to separate with a charge between them in the first place?
 

nsaspook

Joined Aug 27, 2009
8,382
The wool and wax are separate , and have a voltage difference , as they are brought closer together the voltage may be great enough for a small spark to jump ... suppose the voltage difference was 2KV at about 2mm a spark will occur and the two should be at the same potential..

Either way by the time they touch they should be at the same potential ... the copper wire just allows discharge at a great distance.

This brinks up the question if contact allows discharge , how was it possible for them to separate with a charge between them in the first place?
The charge was first separated at a common contact area usually as electrons move to neutralize a local charge imbalance from rubbing or other mechanical motion. Then the contact area is separated by air with further mechanical motion.
 

WBahn

Joined Mar 31, 2012
26,398
The wool and wax are separate , and have a voltage difference , as they are brought closer together the voltage may be great enough for a small spark to jump ... suppose the voltage difference was 2KV at about 2mm a spark will occur and the two should be at the same potential..

Either way by the time they touch they should be at the same potential ... the copper wire just allows discharge at a great distance.

This brinks up the question if contact allows discharge , how was it possible for them to separate with a charge between them in the first place?
When two dissimilar materials are in contact, the atoms at the boundary have different degrees of attraction for the nearby electrons so you can imagine that, on average, more electrons are slightly on one side of the boundary than the other. When the materials are moved apart the excess electrons try to move back to the "correct" side of the boundary but some of them don't make it before the distance is too great and they get stranded, leaving both materials with a net electric charge. This is true even with a simple touch and remove, but rubbing them together essentially results in lots and lots of local "touch and remove" points allowing a significant amount of net charge to build up.
 
Top