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Fundamental definitions - please help

  1. Nov 9, 2006 #1
    Hello.... I've just recently started studying physics for my A levels and i am finding its concepts very hard to get a handle on :frown: .

    One major area im having problems with is my definitions of some of the fundamental properties of electrical circuits. For example i find charge very hard to define.

    I am of course aware that opposite charges repel and like charges attract, but is one area of charge relative to another i.e. if you have an area of charge and an another area of charge which is more negative does that infer a positive charge upon the first. I am also unable to understand how/why a difference in charge generates a force (e.g. the attraction and repulsion of static charges)

    I have other questions, but if you could answer these first i would be very grateful :smile:.

    (Could you also explain in a simple as way as possible, i have viewed some other posts and find them very hard to follow, thanks)
  2. jcsd
  3. Nov 9, 2006 #2


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    [Charge is absolute, not relative, and it is quantized, which means it comes in multiples of some small amount of charge. A negative charge is a negative charge and a positive charge is a positive charge. In most cases of interest, the charges that caue the effects we are familiar with are the negative charge of the electron, and the equal but opposite positive charge of the proton.

    There are many things related to charges and their movement that are relative, but not the charges themselves. A concentration of one kind of charge near a neutral conductor will cause the charges in the conductor to move so that the side of the conductor near the outside charge has a net charge of opposite sign to the outside charge, while the other side of the conductor has a net charge of the same sign as the outside charge. Although overall the conductor is still neutral it will be attracted to the outside charge because the opposite charges are closer together than the like charges. If the conductor touches the outside charge, or a spark is created, the conductor will no longer be neutral. It will either gain some of the outside charges, or lose some of the opposite charges that had built up at one side. An object can be more positive or more negative than another object, and it can behave differently depending on what kind of charge it is near. The net charge of an object can be changed by adding or taking away some of its charge, but at any one time the net charge on the object is either positive, or negative, or neutral

    Why charges exert forces on one another at all, and why there are only two kinds of charge, are some of the great questions physicists have grappled with since charge was discovered. These are important questions, but you already have a great deal to learn about how charges behave given the observations that they do exist, do exert attractive and repulsive forces on one another, and come in two different varieties,
    Last edited: Nov 9, 2006
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