resistivity problem help?
2) Determine at what temperature copper will have the same resistivity as tungsten does at 27°C.
b ) A power station delivers 520 kW of power at 12,000 V to a factory through wires of total resistance of 2.5 Ω. How much less power is wasted if the electricity is delivered at 54,000 V rather than 12,000 V?
Answers & Comments
Verified answer
per wiki, Δρ = α ΔT ρo
alternate form: ρ = ρo [1 + α ΔT]
5.60E-08 = 1.68E-08 [1 + 0.0039ΔT]
ΔT = 598.2905983, T= 625.3C
http://en.wikipedia.org/wiki/Resistivity
Here's a similar problem:
http://answers.yahoo.com/question/index?qid=200702...
The tempco is not really linear; here is the real answer: http://hypertextbook.com/facts/2004/BridgetRitter....
Power is inversely proportional to square of voltage.
12²/54² = 5% as much power wasted.