). In the lab, you apply a certain voltage along a piece of wire and determine t

Question

). In the lab, you apply a certain voltage along a piece of wire and determine the current and the current density through the wire. You then repeat the experiment using a second piece of wire with the same composition and length, but with a different diameter. What differences do you see between the two experiments? (a) Current is the same; current density is different *(b) Current is different; current density is the same (c) Current and current density are both different (d) Current and current density are both the same

Explanation / Answer

We know that, current and current density is given by

I = V/R ; J = I/A

R = rho L/A

I = V A / (rho L)

Since Resistance varies with Area, so the resistance will change, and since Current has an inverse propotionality with reistance, current will also change.

Current density = J = I/A

J = V A / rho L A = V/ rho L

So the current density will not change with the diameter change.

So correct choice is:

(b) Current is different; current density is the same.

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