lecture20

# lecture20 - Electromagnetic principles Electricity...

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ENGRI 1290 1 Electromagnetic principles Electricity generation Transformers Power transport

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ENGRI 1290 2 Electrical current E When electrons are inside an electric field they start moving because of electrical forces. This flow of electron, or electrical current, has a velocity v. This velocity v is limited by the collisions between electrons and ions present in the material. If n is the number of electrons per cubic meters, then the electrical current density (A/m 2 ) is J=nev e is the elementary charge at 1.6x10 -19 C If the material is a cable of area A then the current in the material is I=JA or I=nevA v e - v v v
ENGRI 1290 3 Electrical power v e - E v v v Let’s look at the total electrical force applied on a group of electrons confined inside a cylinder of cross-section A and length L. If the number of electron per cubic meter is n, then the total number of electrons in this cylinder is F=NeE=(nALe)E N=nAL So the total force is The work of this force is then W=FL=nALeEL What is EL ? EL is the electrical potential V (given in volts) So the electrical work is given by W=nALeV

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lecture20 - Electromagnetic principles Electricity...

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