Resistance & Ohm's Law

  • Thread starter jen0519
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  • #1
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Homework Statement


(a) Assuming a resistivity of 1E13 (horseshoe thing)m, calculate the resistance between the ends of a rubber band that is 19 cm long and 2.2 mm in diameter.


(b) Calculate the resistance between the 'heads' and 'tails' sides of a penny that is 1 mm thick and 2 cm in diameter.


(c) WARNING! Do not try this at home! What is the expected current that each would carry if it were connected across a 108-V power supply?
rubber band (A)
penny (A)


Homework Equations



R=pL/a


The Attempt at a Solution



So I thought for the first one that I would use R =pL/A but I think you have to change some of the numbers and I'm not sure how.
 

Answers and Replies

  • #2
berkeman
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Homework Statement


(a) Assuming a resistivity of 1E13 (horseshoe thing)m, calculate the resistance between the ends of a rubber band that is 19 cm long and 2.2 mm in diameter.


(b) Calculate the resistance between the 'heads' and 'tails' sides of a penny that is 1 mm thick and 2 cm in diameter.


(c) WARNING! Do not try this at home! What is the expected current that each would carry if it were connected across a 108-V power supply?
rubber band (A)
penny (A)


Homework Equations



R=pL/a


The Attempt at a Solution



So I thought for the first one that I would use R =pL/A but I think you have to change some of the numbers and I'm not sure how.
Welcome to the PF. Yes, that is the correct equation to use. You are given the resistivity rho, and just need to use the dimensions you are given to get the length L and the cross-sectional area A. Be careful with your units...

And for the penny, you will need to look up the resistivity rho number of copper.
 

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