A cylindrical aluminum pipe of length 1.36 m has an inner radius of 1.80 10-3 m and an outer radius of 3.00 10-3 m. The interior of the pipe is completely filled with copper. What is the resistance of this unit? (Hint: Imagine that the pipe is connected between the terminals of a battery and decide whether the aluminum and copper parts of the pipe are in series or in parallel.)(adsbygoogle = window.adsbygoogle || []).push({});

Here is what I did:

L = 1.36 m

ri = 1.80e-3m

ro = 3.00e-3 m

R = ? ohms

R = pL/A

pcopper = 1.72e-8 ohm*m

palum = 2.82e-8 ohm*m

In = copper

Out = aluminum

Ai = pi*ri^2 = 1.01788e-5 m^2

Ao= pi*ro^2 = 2.827e-5 m^2

Ri = pcopper * L/Ai = .002298 ohms

Ro = palum * L/Ao = .0013566 ohms

Then I did

1 / ( (1/.002298ohms) + (1/.0013566 ohms) )

and got 8.53e-4 Ohms, but it was wrong...

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Electric pipe

**Physics Forums | Science Articles, Homework Help, Discussion**