The terminals of a 0.70 vwatch battery are connected by a 80.0-m-long gold wire with a diameter of 0.200 mm what is the current in the wire? express your answer using three significant figures.

Explanation:

Let's use Ohm's law:

or

  (1)

Where:

We know the value of the voltage V, so we need to find the value of R in order to find I. Fortunately there is a relation between the resistivity of a conductor and its electrical resistance given by:

   (2)

Where:

Keep in mind that the electrical resistivity of the gold is a known constant which is and the cross sectional area of the conductor is calculated as:

Because we have a wire in this case, so we assume a cylindrical geometry.

Now replacing our data in (2)

Finally, we know R and V, so replacing these values in (1) we will be able to find the current:

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explanation: