A copper wire has a diameter of 0.5 mm and resistivity of 1.6 × 10^-8 Ωm. What has to be the length of this wire so that its resistance becomes 10 Ω? How much will the resistance change if the diameter is doubled?
Anonymous:
what's the answer. .?
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i don't know the answer.
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Answers
Answered by
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hey mate!!
apply formula
R = rho l/ A
putting all those given values
l = RA/ rho
Area = pi r^2 = 3.14 * 0.25 *0.25*10^-6
l = 10* 3.14 * 0.25 *0.25*10^-6/ 1.6*10^-8
l = 1.9625 * 10^-6/1 .6 *10^-8
l = 1.23 *10^2
l = 123m
now,
if diameter is doubled I.e radius becomes 4 time.
( for same length)
R' = R/ (4) ^4
R' = R/256
apply formula
R = rho l/ A
putting all those given values
l = RA/ rho
Area = pi r^2 = 3.14 * 0.25 *0.25*10^-6
l = 10* 3.14 * 0.25 *0.25*10^-6/ 1.6*10^-8
l = 1.9625 * 10^-6/1 .6 *10^-8
l = 1.23 *10^2
l = 123m
now,
if diameter is doubled I.e radius becomes 4 time.
( for same length)
R' = R/ (4) ^4
R' = R/256
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