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=Charging Methods= Any time the atoms from one object lose electrons to another object's atoms, the objects are considered charged. Certain materials have a better ability to be charged than others. Charging ability is based around how much electrical affinity the atom possesses, or how attracted the atom is to grabbing other electrons. On this wikipage we will explain the several methods of giving objects a charge; these methods are simply charging by friction, conduction, and induction.

=Charging By Friction= The most common method of transfering charge is through friction. Simply put, when an object composed of atoms that are likely to give up their electrons is rubbed against an object more likely to take electrons, th e objects become charged. For example, imagine a rubber balloon and a piece of animal fur; the rubber balloon is much greater attraction to electrons than animal fur. When these two objects are rubbed together, the electrons attached to the atoms in the animal fur are ripped off by the atoms in the rubber balloon. After the electrons are transfered, the balloon becomes positively charged where the animal fur becomes negatively charged. This explains why when two balloons are charged by animal fur, they repel each other when brought close together.

When rubbed upon a person's head, the balloons became charged as electrons are transferred from the person's fur to the balloons. Since the person's fur lost electrons, it became positively charged and the subsequent attraction between the two rubbed objects could be observed. Of course, when the person pulls away from the balloons, the balloons experienced a repulsive interaction for each other. © Tom Henderson [|Charging by Friction]

= = =Charging By Conduction= Charging by conduction involves the contact of a charged object to a neutral object. Suppose that a positively charged aluminum plate is touched to a neutral metal sphere. The neutral metal sphere becomes charged as the result of being contacted by the charged aluminum plate. Or suppose that a negatively charged metal sphere is touched to the top plate of a neutral [|needle electroscope]. The neutral electroscope becomes charged as the result of being contacted by the metal sphere. And finally, suppose that an uncharged physics student stands on an insulating platform and touches a negatively charged Van de Graaff generator. The neutral physics student becomes charged as the result of contact with the Van de Graaff generator. Each of these examples involves contact between a charged object and a neutral object. In contrast to induction, where the charged object is brought near but never contacted to the object being charged, conduction charging involves making the physical connection of the charged object to the neutral object. Because charging by conduction involves contact, it is often called charging by contact. Charging by Conduction Using a Negatively Charged Object To explain the process of charging by contact, we will first consider the case of using a negatively charged metal sphere to charge a neutral needle electroscope. Understanding the process demands that you understand that like charges repel and have an intense desire to reduce their repulsions by spreading about as far as possible. A negatively charged metal sphere has an excess of electrons; those electrons find each other repulsive and distance themselves from each other as far as possible. The perimeter the sphere is the extreme to which they can go. If there was ever a conducting pathway to a more spacious piece of real estate, one could be sure that the electrons would be on that pathway to the //greener grass// beyond. In human terms, electrons living in the same home despise each other and are always seeking a home of their own or at least a home with more rooms. Given this understanding of electron-electron repulsions, it is not difficult to predict what excess electrons on the metal sphere would be inclined to do if the sphere were touched to the neutral electroscope. Once the contact of the sphere to the electroscope is made, a countless number of excess electrons from the sphere move onto the electroscope and spread about the sphere-electroscope system. In general, the object which offers the most space in which to "hang out" will be the object which //houses// the greatest number of excess electrons. When the process of charging by conduction is complete, the electroscope acquires an excess negative charge due to the movement of electrons onto it from the metal sphere. The metal sphere is still charged negatively, only it has less excess negative charge than it had prior to the conduction charging process. Charging by Conduction Using a Positively Charged Object The previous example of charging by conduction involved touching a negatively charged object to a neutral object. Upon contact, electrons moved from the negatively charged object onto the neutral object. When finished, both objects were negatively charged. But what happens if a positively charged object is touched to a neutral object? To investigate this question, we consider the case of a positively charged aluminum plate being used to charge a neutral metal sphere by the process of conduction. The diagram below depicts the use of a positively charged aluminum plate being touched to a neutral metal sphere. A positively charged aluminum plate has an excess of protons. When looked at from an electron perspective, a positively charged aluminum plate has a shortage of electrons. In human terms, each excess positively charged proton is rather discontented. It is not satisfied until it has found a negatively charged electron with which to co-habitate. However, since a proton is tightly bound in the nucleus of an atom, it is incapable of leaving an atom in search of that longed-for electron. It can however attract a mobile electron towards itself. And if a conducting pathway is made between a collection of electrons and an excess proton, one can be certain that there is likely an electron which would be willing to take the pathway. So when the positively charged aluminum plate is touched to the neutral metal sphere, countless electrons on the metal sphere migrate towards the aluminum plate. There is a mass migration of electrons until the positive charge on the aluminum plate-metal sphere system becomes redistributed. Having lost electrons to the positively charged aluminum plate, there is a shortage of electrons on the sphere and an overall positive charge. The aluminum plate is still charged positively, only it now has less excess positive charge than it had before the charging process began. © Tom Henderson [|Charging by Conduction] =Charging By Induction= If you bring a charged object //near// a conducting surface, you will induce electrons to move in the material even though there is no physical contact. Consider the two insu­lated metal spheres, A and B, in Figure 21.7. (a) They touch each other, so in effect they form a single noncharged conductor. (b) When a negatively charged rod is brought near A, electrons in the metal, being free to move, are repelled as far as possible until their mutual repulsion is big enough to balance the influence of the rod. Charge is redistrib­uted. (c) If A and B are separated while the rod is still present, (d) they will each be equally and oppositely charged. This is charging by induction. The charged rod has never touched them, and it retains the same charge it had initially.

© Tom Henderson [|Charging by Induction]