# E & M Lecture 1 - Lecture 1 TOPICS TO BE COVERED...

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Lecture 1 TOPICS TO BE COVERED; Introduction Atomic physics Energy bands Conductors Insulators Coulomb’s law Conservation & quantization of electric charge

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INTRODUCTION We are surrounded by devices that depend on the physics of electromagnetism It is the combination of electric and magnetic phenomena. This physics is at the root of computers, television, radio, telecommunications etc.
Electric Charge Electric charge is an intrinsic characteristic of the fundamental particles making up those objects. It is a property that comes automatically with those particles wherever they exist. The vast amount of charge in an everyday object is usually hidden because the object contains equal amounts of the two kinds of charge: positive charge negative charge With balance-of these charges, the object is said to be electrically neutral (no net charge). If the two types of charge are not in balance, then there is a net charge , we can say that an object is charged . Charged objects interact by exerting forces on one another.

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Example Charge a glass rod by rubbing one end with silk. tiny amounts of charge are transferred from one to the other, slightly upsetting the electrical neutrality of each.
Charges with the same electrical sign repel each other, and charges with opposite signs attract each other. The attraction and repulsion between charged bodies have many industrial applications Examples: electrostatic paint spraying , nonimpact ink-jet printing, and photocopying. Figure shows a tiny carrier bead in a photocopying machine, covered with particles of black powder called toner, which stick to it by means of electrostatic forces. The negatively charged toner particles are attracted from the carrier bead to a rotating drum, where a positively charged image of the document being copied has formed. A charged sheet of paper then attracts the toner particles from the drum to itself , after which they are heat-fused permanently in place to produce the copy.

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Conductors, semiconductors and insulators Conductors Materials with many free electrons. These electrons can easily be made to flow through the material.
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