Posted by Anonymous on Monday, February 25, 2013 at 5:24pm.
A portable electric heater uses 23.8 A of current. The manufacturer recommends that an extension cord attached to the heater receive no more than 2.60 W of power per meter of length. What is the smallest radius of copper (resistivity 1.72 x 108 Ω·m) wire that can be used in the extension cord? (Note: An extension cord contains two wires.)

physics  Elena, Monday, February 25, 2013 at 5:34pm
P =I²R
R =ρL/A= ρL/πr²
P =I² ρL/πr²
r=sqrt(I² ρL/πP)=...
L=2 m, I=23.8 A, P=2.6 W,
ρ= 1.72 x 10 ⁻⁸ Ω
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