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Unformatted text preview: Current, Resistance, Current, Resistance, and Circuits and Circuits Resistance © RHJansen Resistance All conductors have molecular imperfections that slow current. These imperfections act like air resistance in mechanics. Variable: R Units: Ω (ohms) Example: the resistance in the circuit is 2 ohms, R = 2 Ω R = ρΛ Α ρ is the resistivity, a measure of the quality of the material the wire is made of. It will be found in a table in the text. L is the length of the wire. A is the area of the end of the wire. Wires are usually cylinders, so the area of the end is a circle, A = π r 2 . © RHJansen Factors affecting resistance R = ρΛ Α ρ Increasing resistivity increases resistance. A wire made of a material with more imperfections (obstructions) increases resistance. In other words, when resistivity is high the wire is made of bad materials. L Increasing length of the wire increases resistance. This makes sense, since you are increasing the number of obstructions (caused by the resistivity) in the wire....
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 Spring '08
 Packard
 Physics, mechanics, Current, Resistance, Electric charge

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