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Current is flowing with a current density J=480amp/cm2 in a copper wire. Assuming that each copper atom contributes one free electron and gives that Avogadro number =6.0×1023 atoms/mole density of copper =9.0g/cm3. Atomic weight of copper = 64 g/mole. Electric charge =1.6×1019 coulomb. The drift velocity is:
A. 1mm/s
B. 2mm/s
C. 0.5mm/s
D. 0.36mm/s

Answer
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Hint: The ultimate goal is to find the drift velocity, that can be found by the formula vd=Jne meters per second, where J is the current density, n is the charge-carrier number density and e is the charge.
Here, we need to find the number of charge carriers n and the drift velocity J that in turn we can find using the formulae J=IA and n=N×1m×γ respectively.

Formulae used:
1. Current density J=IA amperes per square meter, where I is current and A is the cross-sectional area.
2. Drift velocity vd=Jne meters per second, where J is the current density, n is the charge-carrier number density and e is the charge.
3. Number of charge-carriers, n=N×1m×γ, where N is the Avogadro number, m is the atomic weight of element and γ is the density of element.

Complete step-by-step answer:
We have been given that current density J=480amp/cm2, Avogadro number N=6.0×1023 atoms/mole, density of copper γ=9.0g/cm3, atomic weight of copper m = 64 g/mole, electronic charge e=1.6×1019 coulomb.
Now, we will find the number of charge carriers with the help of formula n=N×1m×γ(i)
Also the current density can be written as J=IA(ii)
And now, if we use the equation (i) and (ii) in the drift velocity formula which is vd=Jne
We will get, vd=JmNeγvd=480×646.0×1023×1.6×1019×9vd=3072086.4×104vd=355.5×104cm/s=0.36mm/s
Hence, option d is the correct answer.

Additional Information:
Current can be defined as the flow of electrically charged particles in the electron-deficient atoms. The amount of flow of this current per unit cross-section area is called the current density and is expressed in amperes per square meter. These electrons attain an average velocity in a material when subjected to an electric field, that is called the drift velocity.

Note: One may get confused with the number of charge carriers and the Avogadro number and may get the wrong answer due to that. So, we must know that n is the number of charge-carriers while N is the Avogadro number.