Physics Learning

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Electric Fields


What do you mind about this picture??

they  are both enjoying the effects of electrically charging their bodies. Wow!! so amazing!

In this chapter, we can learn Electric Fields,,

Electric Fields:

Properties of Electric Charges

Charging Objects By Induction

Coulomb’s Law

The Electric Field

Electric Field of a Continuous Charge Distribution

Electric Field Lines

Motion of Charged Particles in a Uniform Electric Field

A. Properties of Electric Charges

A number of simple experiments demonstrate the existence of electric forces and charges. For example, after running a comb through your hair on a dry day, you will find that the comb attracts bits of paper. The attractive force is often strong enough to suspend the paper.

Another simple experiment is to rub an inflated balloon with wool. The balloon then adheres to a wall, often for hours. When materials behave in this way, they are said to be electrified, or to have become electrically charged.

In a series of simple experiments, it was found that there are two kinds of electric charges, which were given the names positive and negative by Benjamin Franklin (1706–1790). We identify negative charge as that type possessed by electrons and positive charge as that possessed by protons.

Figure 1

(a) A negatively charged rubber rod suspended by a thread is attracted to a positively charged glass rod. (b) A negatively charged rubber rod is repelled by another negatively charged rubber rod.

We can conclude that charges of the same sign repel one another and charges with opposite signs attract one another .

Another important aspect of electricity that arises from experimental observations is that electric charge is always conserved in an isolated system.

That is,

when one object is rubbed against another, charge is not created in the process. The electrified state is due to a transfer of charge from one object to the other.

B. Charging Objects By Induction

Electrical conductors are materials in which some of the electrons are free electrons1 that are not bound to atoms and can move relatively freely through the material; electrical insulators are materials in which all electrons are bound to atoms and cannot move freely through the material.

Materials such as glass, rubber, and wood fall into the category of electrical insulators. In contrast, materials such as copper, aluminum, and silver are good electrical conductors. Semiconductors are a third class of materials, and their electrical properties are somewhere between those of insulators and those of conductors.

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