PS-6.5 Explain how objects can acquire a static electric charge through friction, induction, and conduction.
Static charge: electron, proton
Charging: friction, induction, conduction
To understand static charges you must first understand where static charges come from, what causes them, and what a "charge" is. The word " static" simply means stationary or unmoving. All matter is made up of tiny particles called atoms. These atoms are in turn composed of smaller particles, Protons, Neutrons, and Electrons. Two of these particles, the Protons and Neutrons, make up the nucleus, or central core, of the atom. The electrons occupy the area outside of the nucleus called the electron cloud.
The Protons in the nucleus carry a positive electrical charge. The Neutrons, each about the same size as a Proton, have no charge. This is why they are called Neutrons...they are electrically neutral. The Electrons that occupy the electron cloud each have a negative charge. Electrons are much smaller than Protons or Neutrons. The mass of an Electron is about 1/1832 the mass of a Proton. Diagram "A" below summarizes the characteristics of the three particles. Diagram "B" shows there relative location in an atom
Normally, atoms will have the same number of negatively charged Electrons as they have Positively charged electrons. This gives the atom an overall electric charge of zero, because negative charges cancel positive charges. The atom shown in diagram "B" above has 4 Protons in the nucleus and 4 Electrons in the electron cloud. 4 negative charges exactly cancel 4 positive charges, giving this atom a net charge of 0. (+4) + (-4) = 0
CHARGING BY FRICTION, INDUCTION, AND CONDUCTION
Static charges often occur because of friction when when surfaces rub against each other, like when you walk across the carpet and your shoes rub on the carpet, or when you rub a balloon on a wool sweater. When some surfaces rub against each other, electrons can be rubbed off of the atoms that make up one surface and stick to another. Diagram "C" shows what happens to an atom that loses an electron. The atom becomes positively charged. The net charge of the atom shown in diagram "C" is +1. The net charge of the surface that picks up the electron is now -1 and the two will attract each other...Remember, like charges repel each other and unlike charges attract each other.
Of course, your carpet is not just made up of one atom, and neither are you. If you walk across the carpet you may rub billions of negatively charged electrons off onto yourself. You can pick up a substantial amount of negative charge. When atoms loose electrons they become positively charged. When a surface gains electrons it becomes negatively charged. This negative charge, which consists of negatively charged electrons, is a static charge. The word "static" simply means stationary or non-moving. The negatively charged electrons picked up by the surface now give the surface many static, or stationary, electrons...this is the static charge.
An electrostatic generator is a device that can produce a very strong static charge. When a charged object is brought near an uncharged object, the charged object can induce a static charge in the uncharged object. This process of producing a static charge from a distance is called induction. Diagram "D shows how this happens. When the negatively charged sphere of the electrostatic generator is placed near a page of paper, the negative charge on the electrostatic generator repels any negative charge on the left side of the paper and pushes it towards the right side of the paper. This leaves only positive charged atoms on the left side of the paper. The negatively charged electrostatic generator has induced a positive charge on the left side of the paper. As seen in Diagram "E" the positive and negative charges then attract and the paper is drawn towards the negatively charged sphere of the electrostatic generator. If the paper were to actually touch the negatively charged sphere the negative charges of the sphere would then be transferred to the paper. This process of charge transfer is called conduction. The paper then be repelled by the sphere.
Diagram D Diagram E
I you were to stand next to the electrostatic generator, the electrostatic generator would certainly induce a positive charge on the side of you that is closest. If you were to touch the electrostatic generator, negative charge would move to you and build up all over your surface. You and every hair on your head would become negatively charged. Every hair on your head would then repel every other hair and this is what would happen!
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