Resistance of a piece of metal

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    Metal Resistance
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Homework Help Overview

The discussion revolves around understanding how the resistance of a piece of metal changes when both its length and diameter are halved. The subject area is electrical resistance, specifically focusing on the relationship between physical dimensions and resistance as described by the formula R = ρL/A, where ρ is the resistivity, L is the length, and A is the cross-sectional area.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants express uncertainty about how to relate changes in diameter to changes in area. There is a suggestion to assume the metal is in the form of a round wire. Some participants question how the new area compares to the old area, focusing on the relationship rather than just the change.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of how to calculate the new resistance based on the changes in dimensions. There is an emphasis on comparing old and new resistance values, but no consensus has been reached yet.

Contextual Notes

Participants are working under the assumption that the piece of metal is a round wire, which may influence their calculations and reasoning. There is also a focus on the mathematical relationships involved rather than direct solutions.

05holtel
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Homework Statement




How does the resistance of a piece of metal change if both its length and its diameter are reduced to one half their original values?
Question 1 answers
It is increased to 4 times the original value
It doubles
It remains unchanged
It is halved
It is reduced to 1/4 of the original value

Homework Equations



R = pL/A where P is the resistivity constant

The Attempt at a Solution



I am not sure how to relate the area to change in area
 
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05holtel said:

The Attempt at a Solution



I am not sure how to relate the area to change in area

I think you can assume it's a round wire.
 


they call one dimension a "diameter" , which becomes half
... how does the new Area compare to the old Area ?
(it's not about _change_ , it is about new = "some number" times old)
 


lightgrav said:
they call one dimension a "diameter" , which becomes half
... how does the new Area compare to the old Area ?
(it's not about _change_ , it is about new = "some number" times old)

Assume it's a round wire, with diameter d, the new diameter will be d/2.
old length is L, new length is 2L

Calculate old and new resistance, compare.
 

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