Is resistance in a wire always bad?

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Fill in the Blank Notes



2) The resistance in a wire depends on:



a) resistivity - ρ  a metals structural resistance to electron flow

p. 4 Reference


b) Length (L) of the wire




c) Thickness (Cross Sectional Area) of the wire (A)


Why do powerful

speakers require

thick speaker wire?

[ Flash ]


"Large speakers draw a lot

of current. Thick wires have

lower resistance"



R = ρL/A 

Ex) R, A relationship?




Inverse relationship


R = ρL/A 



Ranking Task

Rank the resistance of the wires below from smallest to largest.








AP Physics B

Giancoli p. 516) 16



L and R are direct

L + 4L = Total Length = 5 L

Cut the wire at 20 % of total length


Since wire R = 10 ohms


R1 = 2 ohms, R2 = 8 ohms





[ Flash ]





3) Resistance and Temperature

(Double Click on Picture above to start video)

Full Size Video


Scientific Advisors: Dr. Saul Dushman; Dr. Roman Smoluchowski; Dr. David Harker

Prelinger Archives

Production Company: Wolff (Raphael G.) Studios, Inc. Audio/Visual: sound, color
Creative Commons license:
Public Domain






T down, R down


T up, R up





(many electrical devices
 have fans to decrease T)




Nonmetals – When temperature increases, resistance decreases 


Superconductor - conductor with no resistance


Achieved only at very low temperatures
(expensive now)









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