Answer to Question #167048 in Electricity and Magnetism for Naomi

Question

Suppose a telephone linking lagos and london is a copper wire length 6000km.if the current in this wire is 0.6mA,what is the velocity electron of the wire?if telephone impulses were to travel the speed ,how long will it take to transmit a message along the line?estimate the actual time take.The diameter of the wire is 5×10^-4m,the number density of copper atoms is 8 4×10^28m^-3 and the speed em wave is 3×10^8ms^-1.

Answer 1

Volume of wire

$V=\pi\frac{D^2}{4}l$

$V=\pi\frac{(0.0005)^2}{4}(6400000) =1.256m^3$

Number of electron

$n=2512(84\times10^{28})=105.5\times10^{28}$

Drift velocity can be obtain as

$V=\frac{I}{neA}$

$V=\frac{0.0006}{(105.5\times10^{28})(1.6\times10^{-19})(1.96\times10^{-7})}\\v=1.8\times10^{-4}m/s$