We first need to get electrons and then to set them in motion so that we can have an electric current.
We saw in the section about batteries that we can extract electrons from a metal by immersing it in an acidic solution. This would be the zinc we immersed in lemon juice. By using a suitable setting that will be attracting the electrons continuously - which would be the copper electrode that attracts the electrons more and that is losing electrons itself - we can generate and maintain an electron flow.
Is there another way we can get electrons? The answer is yes, by friction.
Let us consider the following Wikipedia text:
"A normal uncharged piece of matter has equal numbers of positive and negative electric charges in each part of it, located close together, so no part of it has a net electric charge. The positive charges are the atoms' nuclei which are bound into the structure of matter and are not free to move. The negative charges are the atoms' electrons. In electrically conductive objects such as metals, some of the electrons are able to move freely about in the object."
Based on the ability of charges to move about in the object, materials are distinguished in conductors which allow charges to move freely and insulators which do not.
Note the following text (cf. the greek word for friction is “τριβή")
"Scientists have ranked materials in order of their ability to hold or give up electrons. This ranking is called the triboelectric series."
"A list of some common materials is shown below. Under ideal conditions, if two materials are rubbed together, the one higher on the list should give up electrons and become positively charged."
(end of quote)
So what will happen if we brush our hair with a PVC brush?
Electrons from our hair will move to the PVC brush. Our hair will be positively charged and the brush will be negatively charged
As our hair will be positively charged, each hair will repel the other and we will have a bad hair day!
What happens if we touch a metal door knob? Electrons from the metal will rush to our hair and we will may be ticked by a spark.
An electric current has actually been generated.
Could we take advantage of the friction phenomenon to generate electricity?
We saw in the section about batteries that we can extract electrons from metals by immersing them in acidic solutions.
What about friction? What if we rub a metal? Electrons will move to our hand and the metal will become positively charged. We can therefore “charge” a metal by rubbing it with our hand. If we keep on rubbing it we produce a bigger and bigger charge.
Could we store this charge?
First, here is a setting for a somehow “bigger scale” generation.
A metal ball in rotation; we place our hand on it. Electrons are leaving the ball towards our hand and the ball acquires positive charge which becomes bigger and bigger.
What can we do with the charge that is being accumulated on its surface? Could we store it somewhere? By putting in contact other metals such as a sheet of aluminium foil we could store it there. But could we retrieve it? For instance to light up a lamp?
By using a small chain we can transfer it onto a sheet of aluminium foil. Electrons from the aluminium foil will be attracted from the ball and the foil will become positively charged.
What happens if we approach another sheet near the other? E.g. we put a piece of paper on the first aluminium sheet and on top of the paper another aluminium foil? Then the electrons of the second will be attracted by the positive charges of the first; they would try to “escape” and go onto the first foil due to the attraction. However, as the paper doesn’t let them, this cannot be done. Instead, as the ball is rotating and more positive charge is generated on the first aluminium foil more charge will build up between the two aluminium foil sheets.
This builds up potential between the two foils and actually stores it between the two sheets. If we were to remove the system and connect is with a wire that linked to a light bulb, electrons would flow on the wire and light the bulb!
The system of the two foils provides the notion of the capacitator.
Static electricity explained using EMS for SolidWorks
With a 200kV @ 12" measurement device, the voltage measurements were off the scale and he was still 20 feet away from the web! For the meter to be pegged at that distance, the amount of static electricity had to be in the Megavolt range. He thought to himself "Van de Graaff would be proud!"