Calculate the electric field in a copper wire of cross-section area 2.0 mm2 carrying a current of 1 A. The resistivity of copper = 1.7 × 10–8 Ω m.

8.5mVm-1


Given,


Area of cross-section of wire, A=2.0 mm2=2×10-6 m2


Current flowing through the wire, I=1A


Resistivity of copper, ρ= 1.7 × 10–8 Ω m


Formula used,


From electrostatics, we know that Electric field, E is



Or it can be written as



Where l is the distance over which potential difference V has an effect


From Ohm’s law and the concept of current density, the relation connecting resistance, R and resistivity, ρ can be written as,



Where ‘l’ is the length of the conductor (or wire) and ‘A’ is the area of cross-section of the conductor.


Solution,


We know that potential difference, V is



Using eqn.2, the above expression can be modified as,



Now, in order to find the electric field by eqn.1, we can replace V in eqn.1 with the above expression as,



On simplification, it becomes,



We have all the values for the above expression. So, on substitution, Electric field will be,



Hence the electric field in a copper wire is 8.5mVm-1


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