Answer to Question #265792 in Electric Circuits for Felix

Question

A piece of resistant wire of diametre of 0.8mm and resistant is 6ohm's has a resistivity of 8.8*10^4 metre.calculate the length of the wire take π=22/7

Answer 1

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

Where $R=$ Resistance

$\rho$ $=$ Resistivity

L $=$ Length

A $=$ Cross section area $=\pi\>r^2$

$A=\frac{22}{7}(\frac{0.8}{2}×10^{-3})^2$

$=5.029×10^{-7}m^2$

$l=\frac{AR}{\rho}$

NB: Value of resistivity given in the question is

$\color{blue}{8.8×10^4metres}$

1. The units are wrong

2 The value is unrealistically high for a wire

Taking the value of resistivity as :

$\textcolor{red}{8.8×10^{-4}\>\Omega m}$

$Length=\frac{5.029×10^{-7}×6}{8.8×10^{-4}}$

$=3.429×10^{-3}m$