chapter27_1

chapter27_1 - Chapter 27 Current Resistance And Resistor...

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Chapter 27 Current Resistance And Resistor
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Electric Current, the definition c Assume charges are moving perpendicular to a surface of area A c If Δ Q is the amount of charge that passes through A in time Δ t , then the average current is t Q I avg Δ = or dt dQ I = + + + + + + I A
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Electric Current, definition and unit c Electric current is the rate of flow of charge through some region of space c The SI unit of current is the ampere (A) c 1 A = 1 C / s c And ampere is a base unit. The unit for time, second, is also a base unit. c The unit for charge is then defined as 1C=1A/1s c The symbol for electric current is I
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Direction of Current c The charges passing through the area could be positive or negative or both. This area may or may not be an actual physical surface and the charges can flow in a conductor or in vacuum. c It is conventional to assign to the current the same direction as the flow of positive charges c The direction of current flow is opposite the direction of the flow of electrons c It is common to refer to any moving charge as a charge carrier
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chapter27_1 - Chapter 27 Current Resistance And Resistor...

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