- #1
uby
- 176
- 0
Sorry, I had a long post that just got eaten by my computer so I am having to re-type my question. It will need to be brief:
Here is an example of a van de Graaff generator: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/vandeg.html
It notes that the bottom brush is "given a positive voltage to draw electrons off the belt". I have no idea what this means. How is it given a voltage? A positive voltage relative to what? If it is drawing off electrons, where do these electrons go? Electroneutrality would require that all those electrons drawn ultimately from the metal sphere need to go somewhere. Where is this mythical negatively charged object?
This arrangement ultimately seems like a capacitor to me. Whether by pulleys or by an external power supply, work is inputted into the system to re-arrange electrons. The metal sphere that is positively charged and the mythical negatively charged object create an air-gap capacitor with the energy of the electric field between them maintaining charge separation. This is why electrostatic generators are high voltage: they have such low capacitances! But why then, can charge move all over the metal sphere uniformly, when it should be concentrated in the region of the electric field?
thanks!
Here is an example of a van de Graaff generator: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/vandeg.html
It notes that the bottom brush is "given a positive voltage to draw electrons off the belt". I have no idea what this means. How is it given a voltage? A positive voltage relative to what? If it is drawing off electrons, where do these electrons go? Electroneutrality would require that all those electrons drawn ultimately from the metal sphere need to go somewhere. Where is this mythical negatively charged object?
This arrangement ultimately seems like a capacitor to me. Whether by pulleys or by an external power supply, work is inputted into the system to re-arrange electrons. The metal sphere that is positively charged and the mythical negatively charged object create an air-gap capacitor with the energy of the electric field between them maintaining charge separation. This is why electrostatic generators are high voltage: they have such low capacitances! But why then, can charge move all over the metal sphere uniformly, when it should be concentrated in the region of the electric field?
thanks!