Ch 17 Current and Resistance


Electric Current

Imagine a surface such as a cylindrical wire. Current is as the amount of charge q that flows perpendicular through a surface area A in an amount of time t. Current is measured in Amperes and is defined as one Coulomb of charge moving through an area A per second.

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Current I = Q / t charge / second

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REMEMBER that we can think about current in two different ways! The charge flowing can be considered negative or positive.
Conventional Current is the flow of "positive charge" and the flow of the "HOLES".
Electron flow is the other way of thinking about current and is the flow of negative charge.
Either way- the laws and relationships related to electrical current are valid.

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Resistance and Resistivity

There is resistance to the flow of charge inside of any material. Resistivity is a physical property of a material that when used with the physical dimensions of an object made of the specific material (length and cross-sectional area) will quantify the resistance of the object.

R is the resistance of the object, p (rho) is the RESISTIVITY of the material, l or L is the length, and A is the area

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Explore the relationships between the variables in the resistance formula using the PhET!