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 the equation:

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

where

$\rho$ is the resistivity of the material

L is the length of the wire

A is the cross-sectional area of the wire

In this problem, we have a wire of platinoid, whose resistivity is

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

The length of the wire is

L = 7.0 m

And its radius is

$r=\frac{0.14 cm}{2}=0.07 cm = 7\cdot 10^{-4} m$, so the cross-sectional area is

$A=\pi r^2=\pi(7\cdot 10^{-4})^2=1.54\cdot 10^{-6}m^2$

Solving for R, we find the resistance of the wire:

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