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Home Q & A Board Biology-Related Homework Help General Biology
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klajevar klajevar
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11 years ago
 How does the resistance of a piece of conducting wire change if both its length and diameter are doubled? (a) Triples (b) 6 times as much (c) 8 times as much (d) 1/4 as much (e) None of the above
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11 years ago
Resistance = (Resistivity x length) over cross-section area.

So... Let's start with l = 1 and d = 1

R = r1 / 1 = r1

Let's do l = 2 and d = 2

R = r2 / 2 = r1

As you can tell, doubling both of them will cause it to remain the same.

Take this other example:

A wire has resistance 56.8 ohms. If another wire consists of the same material but has twice the length and half the diameter of the first, what is the resistance of the 2nd wire?

Answer: Resistance = rho * L/A where rho = resistivity of the material, so it's the same for both wires.

You've doubled the length, and you've divided the area by a factor of 2^2 = 4. Calculate rho * (2L)/(0.25A) and compare that to rho * L/A.
samtheman125
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