Calculating combined resistance of wires

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Homework Help Overview

The discussion revolves around calculating the combined resistance of six copper wires and a steel core, with a focus on the implications of different materials on resistance values. The original poster expresses uncertainty about their approach and the exclusion of the steel core in their calculations.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the method for calculating net resistance in parallel circuits and question the rationale behind excluding the steel core from the resistance calculation. There are attempts to clarify the calculations involved and the implications of using different materials.

Discussion Status

The conversation is ongoing, with participants exploring various interpretations of the problem and the calculations involved. Some guidance has been offered regarding the correct approach to calculating resistance in parallel, and there is a recognition of the need to consider the type of wire used.

Contextual Notes

Participants note that the wires are in a parallel connection and that resistance values are provided, which may influence the calculations. There is also mention of a previous discussion on this topic, indicating a potential for revisiting established concepts.

toforfiltum
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Homework Statement



upload_2015-5-22_8-19-31.png

Homework Equations


  • R ∝ 1/A

The Attempt at a Solution


Since there are six copper wires and a steel core, I added the resistance of all the wires and the core and divided them by 7, though I don't think my approach is right since the resistance of the copper and steel wires are different. As such my answer is about 22.9Ω, which is wrong. The answer is B, 1.6Ω, which is just the quotient of the the total resistance of the six copper wires. Why is the resistance of steel core not taken into account in this case?
 

Attachments

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Do you know how to calculate the net resistance of resistors in parallel?
 
Ermm...yes. But why is the steel not taken into account?
 
toforfiltum said:
Ermm...yes. But why is the steel not taken into account?
Why are you so sure it isn't? Have you done the calculation taking the steel into account?
 
Oh, so is the working 6(1/10) + 1/100 correct for 1/R?
 
toforfiltum said:
Oh, so is the working 6(1/10) + 1/100 correct for 1/R?
Yes.
 
Thanks. So is this combined resistance of six different copper wires and steel less than a power cable just made up of one copper wire of the same cross-sectional area?
 
toforfiltum said:
Thanks. So is this combined resistance of six different copper wires and steel less than a power cable just made up of one copper wire of the same cross-sectional area?
What do you think?
 
I think the resistance of six different copper wires and the steel would be lesser. However if it's just the six copper wires without the steel, then they would be the same.
 
  • #10
toforfiltum said:
I think the resistance of six different copper wires and the steel would be lesser. However if it's just the six copper wires without the steel, then they would be the same.
Quite so.
 
  • #11
Why quite so? Is it not really correct?:smile:
 
  • #12
toforfiltum said:
Why quite so? Is it not really correct?:smile:
"Quite so" means, yes, that is exactly correct. (British English idiom?)
 
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  • #13
Oh I see.
 
  • #14
Since resistance values are given we need think about type of wire.
From situation they are in parallel connection.
Please see the attachment
 

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  • #15
Neelima said:
Since resistance values are given we need think about type of wire.
From situation they are in parallel connection.
Please see the attachment
Yes, the OP got this in post #5. Five years ago.
 
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