SOLUTION: At a fixed temperature, the resistance, R. Of a wire varies directly as the length, l, and inversely as the square of its diameter, d. If the resistance is 0.75 ohm when the diamet

Question 979479: At a fixed temperature, the resistance, R. Of a wire varies directly as the length, l, and inversely as the square of its diameter, d. If the resistance is 0.75 ohm when the diameter is 2 mm and the length is 3000 cm, what is the resistance when the diameter is 5 mm and the length is 2000 cm?
Found 2 solutions by Boreal, Alan3354:
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
R=L * d^2
0.75ohm=k*3000cm*4mm^2, where k=constant
0.75/12000=k=0.0000625
R=k*2000cm*25mm^2*0.0000625=3.125 ohms ANSWER
Check:
diameter has increased by 2.5 and square by 6.25
length has decreased by 1/3 and is 2/3 of what it was
the resistance should change by a factor of (25/4)(2/3)=50/12 or just over 4 times
3.125 is just over 4 times 0.75.

Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
If the resistance is 0.75 ohm when the diameter is 2 mm and the length is 3000 cm, what is the resistance when the diameter is 5 mm and the length is 2000 cm?
------------
R1 = k*3000/2^2 = 0.75
k = 0.001
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R2 = k*2000/5^2
R2 = 0.08 ohm
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