Question involving resistivity using the formula?

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Homework Help Overview

The discussion revolves around calculating the length of nichrome wire needed to achieve a specific resistance, given its resistivity and diameter. The problem involves understanding the relationship between resistance, resistivity, length, and cross-sectional area.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants explore the formula for resistance and question the meaning of "area" in the context of the wire's diameter. There are attempts to clarify unit conversions and the calculation of the cross-sectional area.

Discussion Status

Some participants have provided guidance on interpreting the formula and calculating the area of the wire's cross-section. There is a recognition of potential unit confusion, and multiple interpretations of the problem are being discussed.

Contextual Notes

Participants note that the diameter is given in millimeters, which may lead to confusion regarding unit conversions. The resistivity is specified in micro ohm meters, adding another layer of complexity to the calculations.

einstein101
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Homework Statement



The resistivity of nichrome wire is 1.1micro ohm meters. What length of wire of diameter 0.079 mm is required to provide resistance of 1.0 Kohm?

Homework Equations


R=resistivity x length/area


The Attempt at a Solution



1000ohms = ? x 0.0011/0.079

79 = ? x 0.0011

71818.18 = resistivity

I know I've stuffed up real bad, but this one is troubling me crazy.
 
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einstein101 said:

Homework Statement



The resistivity of nichrome wire is 1.1micro ohm meters. What length of wire of diameter 0.079 mm is required to provide resistance of 1.0 Kohm?

Homework Equations


R=resistivity x length/area

What does "area " mean in the formula for resistance? What is the area for the 0.079 mm wire?

ehild
 
Area relates to the 0.079 mm of wire. In the question it doesn't say mm squared. the answer is supposed to be 4.5 meters.
 
The diameter of the wire is 0.079 mm. The cross-section of a wire is a circle usually. The area in the formula means the area of the cross section of the wire. ehild
 
I got 4.5m for the length.
I think you have mixed up the units.
resistiuvity = 1.1x10^-6ohm.metre
radius of wire = 0.0395x10^-3m
 
Thanks Emily I got the answer too now. You were right I was mixing the units up.
 
Hey Einstein...thanks...great help someone else
 

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