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Charges

The chapter on charges allows us for the first time to look into what cause for a specific force – the electrostatic force.

When you take clothes out of the dryer you might have noticed how they cling together. There is an attractive force between two pieces of clothes (that Bounce tries to reduce) that you would have difficulty explaining with all your knowledge thus far. The force is not gravitational, nor is anything pushing or pulling on the clothing. Therefore the force must be caused by a new quality that some objects have and this quality is called “charge”. It is important that the name is simply given to the “thing” the “quality of the object” that causes the attractive force.

What we are doing in the chapter on electrostatics is to peel away another layer of the phenomena that surround to gain a better understanding of the world. This is by far not the final layer of the “mystery” of charges but we are getting closer to the core.

When we looked at falling objects for instance, we first simply described their motion. Then we looked for the reason these objects fall and gave it the name gravitational force. That is different from “gravity” which was the acceleration that just helped us to describe the falling object. We never asked the question: “What causes gravity?”. We never investigated whether certain objects have a quality that causes them to be attract or attract other objects. This is, however, what we are doing now. We are investigating charges more, because a lot of chemistry is based on them.

 In class we did an experiment with Scotch tape that let us to conclude that there are different charges that cause objects to either attract or repel. These charges are labeled positive and negative. Then there is a third type of object that is attracted to either positive or negative charges. Since most other objects, unless they are charged before, belong to this third group they are called neutral. Like charges attract and unlike (positive and negative) charges attract. Neutral object are attracted to either charge. The process by which this happens depends on whether the neutral object is a conductor or an insulator. Conductors have charges that are free to move around. These charge are called electrons and are negative. The protons or positive charges are always bound to the nucleus of the atom and cannot move freely.

When a conductor is brought close to a negative charge, the electrons that are free to move will move away from the charge as far as they can. That creates a situation where there are more negative charges are in one region of the conductor and fewer in another. The region that has too many electrons is negatively charged, the other region positively, because of lack of electrons. The positive region since it is closer to the charge will be attracted to this charge. This process is called induction.

 When an insulator is brought close to a negative charge the attraction will be caused by a different interaction. Since the electrons cannot move around freely but still want to move away from the negative charge they will stay bound to the proton but flip around so they are as far away from the negative charge without leaving the atom and the proton they are bound to.    This process is called polarization.

.With the model of charge we have a way to predic which objects attract and which repel one another and in addtion are able to explain why neutral objects are always attracted to charged objects.

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