A wire of length 1 m. has a resistance of 0.30 ohm. It is uniformly stretched to a length of 2 m. What is its new resistance.
Answers with explanations pls, thank you, i don't know how to relate the old resistance to the new one...
2007-12-15 19:31:51 · 3 answers · asked by Sammy Baby 1 in Science & Mathematics ➔ Physics
Resistance is proportional to length, and resistivity (rho) and inversely proportional to area. By doubleing the length, the resistance should double.
Thus the resistance in the new wire is 0.60 ohm.
Resistiance = (Resistivity x length)/Area
NOTE: In this question, assuming the cross sectional area remains constant in the wire "A" should not change.
2007-12-15 19:51:21 · answer #1 · answered by Vu T 2 · 0⤊ 0⤋
The answer depends on how you treat the stretching of the wire. If you include the fact that the diameter decreases as the wire is stretched, you must know Poisson's ratio for the material. Since that information was not given, then perhaps you were not supposed to take that into account. The resistance of a wire is rho*L/A, where L = length and A the cross-sectional area. If A does not change, then the resistance increases linearly with A, so that doubling the length (from 1 to 2 m) doubles the resistance (to 0.60 ohms).
2007-12-16 03:53:35 · answer #2 · answered by gp4rts 7 · 0⤊ 0⤋
you should use this formula: R=(gL/A)
"g" is specific resistance
"L" is the length of sample
"A" is the area of it
g is constant,so is not important.
R1 / R2= L1A2 / L2A1
but you should know what the A is.I mean if it is circular.triangle,...
2007-12-16 03:56:14 · answer #3 · answered by sata 2 · 0⤊ 0⤋