SOLUTION: The electrical resistance r of a wire varies directly with its length l and inversely with the square of its diameter d. 100 m of wire with diameter 3 mm has resistance of 8 ohms.

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Question 1156584: The electrical resistance r of a wire varies directly with its length l and inversely with the square of its diameter d. 100 m of wire with diameter 3 mm has resistance of 8 ohms. What is the resistance of 150 m of wire with diameter of 4 mm?
Found 2 solutions by mananth, Edwin McCravy:
Answer by mananth(16946) About Me  (Show Source):
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The electrical resistance r of a wire varies directly with its length l and inversely with the square of its diameter d. 100 m of wire with diameter 3 mm has resistance of 8 ohms. What is the resistance of 150 m of wire with diameter of 4 mm?
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r = k*(l/d^2)
l = 100m diameter = 3mm = 0.003m , r = 8 ohms
k = r * d^2/l
k = 0.003^2*8/100
k= 7.2*10^-7
150m, d=0.004m, k= 2.4*10^-7
r= 7.2^-7*150 /(0.004)^2
r= 9.35 ohms

Answer by Edwin McCravy(20060) About Me  (Show Source):