Love this! I do take some issue with your explanation of electric flux density lines - particularly from 4:20 - 5:30. You seem to be implying that electric flux density always occurs in dipole pairs with the talk of lines starting on positive charges and terminating on negative charges and with description of the electric flux lines between the gold leaf and the stiff conductor. But unlike magnetic fields, we do have electric monopoles. Negative charges are like "sinks" and positive charges are like "sources" (to use a fluids analogy). However, the fields between the gold leaf and the stiff conductor are the superposition of the fields that arise due to the negative charges on each (no real need to worry about positive charges). Thus, the fields between the gold leaf and the stiff condutor mostly cancel out. Meanwhile, the fields on the upper left side of the gold leaf are oriented toward the gold leaf (orthogonal to it). Likewise, the fields on the right side of the stiff conductor are oriented toward the stiff conductor (and orthogonal to it). The electrons are pulled in the direction opposite of the electric field. Thus, the gold leaf deflects upward to the left. (The stiff conductor would likewise deflect to the right if it were not being held in place by apparatus and the stiffness of the stiff conductor).
Thank You so much for this wonderful video. It helped so much in understanding the concept clearly in a step-by-step manner. Thnx a lot for this wonderful demo.
Hello , my name is Gilvan Pirôpo , I am Brazilian and I need to build an electroscope like this first appearing in the video , with wooden frames , could you give me any tips of the materials I need. Thank you very much in advance.
+Gilvan Pirôpo Here is a link to where you can get a pdf of a 100 year old book entitled, The Boy Electrician. In Chapter II Static Electricity, the author describes how to build an electroscope. You have to go to the link in the second message on this page, the first one does not work. brassgoggles.co.uk/forum/index.php?topic=35144.0
hello, prof. Melloch. If the flame of a candle is brought close to a charged electroscope , the air surrounding the electroscope becomes a conductor!, and the charge from the electroscope leaks to surrounding bodies.
I'm trying to understand what is going on at 3:19. Just when you remove the rod, for an instant the leaves come together again, just to come apart in the next moment. Do you know why that happens? I don't see how it fits the model. Thank you
Great observation. I went back and verified the behavior. When I tried it with an electrophorus (ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Sqhgrw3bDmU.html) instead of the PVC tube the leaves did not come together as the electrophorus was removed. I'm a little puzzled by the behavior with the PVC tube and will have to think about it.
Why is it that when you are holding the PVC rod the negative charge doesn't go to your body through your hand, but when you touch the electroscope it does?
How do charges more around the insulator rod? As an insulator, it should not allow charges to move through or on its surface. When you touch the rod to the neutral electroscope, is the transferring charge collected from the entire length of the rod or just the point of contact? According to what you are saying, only the charge congregated at the point of contact should move over to the electroscope. Thanks, I am trying to understand this to help my son with his science test :)
Yes when the rod touches the electroscope it will just be some of the charge, where the contact is being made, which will transfer from the rod to the electroscope. So the rest of the rod will remain negatively charged.
FWIW, the choice of gold, as an electrically conductive material, is not necessarily relevant. Traditionally (100 to 200 years prior), gold was chosen as a highly malleable material (i.e. "formable", without cracking)... which allowed "hammering" gold into very thin foil; reducing mass (weight/inertia) and therefore easily moved by small forces (electrostatic and/or air currents)... along with reducing spring tension stiffness... also easily move-able by small forces. Furthermore, gold is non-magnetic. Metallized Mylar (metallic shiny balloons/or anti-static packaging for sensitive electronics) could be equally effective (even Graphene?)
No, you are wrong! When you touch it, you transfer electrons in to the wire and when you remove field you have excess electron charge vs ground and that is why foil repels... There are no positive nor negative charges, just electrons...
Before I touched the electroscope, the PVC tube has excess electrons, and hence a net negative charge, and the electroscope is neutral. So there is a net negative charge between the PVC tube and the electroscope. When I touch the electroscope, electrons cannot flow onto the electroscope because the system has a net negative charge. Instead electrons will flow from the electroscope, repelled by the net negative charge, through my finger onto me. I am large enough compared to the system of the PVC tube and electroscope that I function as a ground. When I remove my finger the electroscope now has a deficit of electrons, which means the electroscope is positively charged. There are more protons (positive charges) on the electroscope than electrons (negative charges).
