Splung.com Physics Forum
Discuss physics or ask questions. Part of the Splung.com physics web site.

Author Message
roxiney

Joined: 15 Sep 2010
Posts: 5
Location: north carolina

 Posted: Thu Sep 30, 2010 9:13 pm    Post subject: Radius and Resistance Two conductors are made of the same material and have the same length L. Conductor A is a hollow tube with inside diameter 1.29 mm and outside diameter 2.55 mm; conductor B is a solid wire with radius RB. What value of RB is required for the two conductors to have the same resistance measured between their ends?
hepcj

Joined: 23 Jun 2007
Posts: 125

 Posted: Thu Sep 30, 2010 9:58 pm    Post subject: The resistivity is rho = R A/l The wires have the same length. You need to calculate the area of the anulus forms by the cross-section of the hollow wire. This is the circular area of the outer radius minus the circular area of the inner radius RB. (A = pi * RB^2) Then to find the radius of the equivalent solid wire. RB = sqrt(A/pi)
roxiney

Joined: 15 Sep 2010
Posts: 5
Location: north carolina

 Posted: Thu Sep 30, 2010 10:09 pm    Post subject: How do you fins A if you are not given a length?
hepcj

Joined: 23 Jun 2007
Posts: 125

 Posted: Fri Oct 01, 2010 6:23 pm    Post subject: The length is the same for both conductors and it is not used in the cross-sectional area. The cross-sectional area only depends on the radius. A = pi * r^2 for a circular cross-section. For a tube shape, A = pi*(r_outer^2 - r_inner^2).
 Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First
 All times are GMT Page 1 of 1

 Jump to: Select a forum Physics Forum----------------Physics Help. Ask a Physics ExpertPast Papers
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum