Resistance in a Wire

Is resistance in a wire always bad?

School blocks YouTube? Use the file below.

bulbResistance.mp4

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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"

Ex) R, A relationship?

Inverse relationship

4 

[ 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

Metals

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)

R, Wire Questions