Understanding electro static experiment

Thread Starter


Joined Oct 3, 2023
Hey guys,
I'm trying to find the following experiment : two cans are put aside and a small metal object is put in between(see below picture). When the PVC pipe is rubbed it thus induces electrons in the system. The metal object then starts to be attracted to one can and then seems to be attracted to the other.

I'm trying to properly understand what's happening in there. Why is the metal object at first attracted to one of the cans ? Also why is it then being attracted(or repelled ) to go on the other can?Also, one of the cans is isolated on what seems to be some sheet of papers. How does this influence the experiment ?

Thanks a lot for your help guys.

You can also view the experiment in the following video at 20 seconds :



Joined Mar 31, 2012
Since this is Homework Help, what exactly is the assignment you are trying to complete. That will help us give you more effective assistance.


Joined Mar 31, 2012
Without watching the video, this is what I would expect to happen.

When you rub the PVC pipe it becomes electrically charged. For the sake of discussion, let's say that some electrons are transferred from the pipe to the cloth so that the pipe is positively charged.

When you move the pipe near one of the cans, the positive charges on the pipe attract electrons in the can toward the pipe, so that side of the can becomes positively charged. But, assuming that the can is sitting on a table that is sufficiently non-conducting (or sitting on an insulating spacer, perhaps), the total charge on the can can't change (much) and so the electrons on the side near the pipe are at the expense of electrons on the other side of the can, resulting in that side of the can being positively charged.

Now the same thing happens with the metal tab -- the positive side of the can attracts electrons to the near side of the tab, but since the tab can move, the negative-charged side of the tab is attracted to the positively-charged side of the can. If the attraction is sufficient, they will touch, but that will transfer electrons from the tab to the can, resulting in the tab having a net-positive charge, Even though the can now has a net-negative charge, the pipe is still pulling enough electrons to the other side of the can to result in the side of the can near the tab being positive charged, and thus the tab is repelled away from it. But if it touches the other can (which, ideally, is grounded), then the tab will dump the charge (by pulling electrons from the grounded can) and the cycle can repeat. This will only happen for a while, because with each cycle the first can is becoming increasing negatively charged and eventually this will stop the process until is it discharged.