Question

Taking the resistivity of platinoid as 3.3 x 10-7 m, find the resistance of 7.0 m of platinoid wire of average diameter 0.14 cm.

Answer 1

Answer:

$1.5 \Omega$

Explanation:

The resistance of a wire is given by:

$R=\frac{\rho L}{A}$

where

$\rho$ is the resistivity of the material

L is the length of the wire

A is the cross-sectional area of the wire

For the wire in this problem:

$\rho = 3.3\cdot 10^{-7} \Omega m$

L = 7.0 m

r = d/2 = 0.07 cm = 0.0007 m, so the area is

$A=\pi r^2=\pi(0.0007)^2=1.54\cdot 10^{-6}m^2$

Solving for R,

$R=\frac{(3.3\cdot 10^{-7})(7.0)}{1.54\cdot 10^{-6}}=1.5 \Omega$