Question

An 18-gauge copper wire (diameter 1.02 mm) carries a current with a current density of 1.70106 a/m2 . Copper has 8.51028 free electrons per cubic meter.

Answer 1

Part A  

Calculate the current in the wire.  

Part B  

Calculate the drift velocity of electrons in the wire

I = J*pi*d^2 / 4  

=1*10^6*pi*0.00102^2 / 4  

I= 0.90 A  

Part B:  

Vd= J / nq  

where n=8.5*10^28  

q=1.6*10^-19  

= 1*10^6 / [(8.5*10^28)(1.6*10^-19)]  

Vd = 8.1*10^-5 m/s