SOLUTION: I am not good with word problems so can someone help? The electrical resistance R of a wire varies as its length L and inversely as the sqaure of its diameter. A wire 20 meters

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: I am not good with word problems so can someone help? The electrical resistance R of a wire varies as its length L and inversely as the sqaure of its diameter. A wire 20 meters      Log On


   

Question 65557: I am not good with word problems so can someone help?
The electrical resistance R of a wire varies as its length L and inversely as the sqaure of its diameter. A wire 20 meters long and 0.6 centimeters in diameter made from a certain alloy has a rsistance of 36 ohms. What is the resistance of a piece of wire 60 meters long and 1.2 centimeters in diameter made from the same material?
Ok so I analyzed the problem and I know that the key words here are:
Resistance varies directly in length and inversely as the square of it's diameter
36 ohms=20 meters long and .6 in diamter
? ohms=60 meters long and 1.2 in diameter
Both have same material.
We are trying to find resistance to the second set of numbers.
Answer by 303795(602) About Me  (Show Source):
You can put this solution on YOUR website!
The resistance varies directly with length so the second wire is 3 times as long so it will have 3 times the resistance 36 * 3 = 108 ohms. This assumes the second wire has the same diameter but it doesn't.
The resistance varies as the inverse of the square of the diameter. The second wire is twice the diameter of the first. Square 2 to get 4. The inverse of 4 is 1/4 so the resistance will be 1/4 of 108 ohms = 27 ohms.