00:01
We have a gold wire that has a diameter of 0 .87 millimeters.
00:07
We're going to convert this to radius by dividing by 2, and you get 0 .435 millimeters.
00:13
Divide by 1 ,000 to get to meters, and so you have 4 .35 times 10 to the negative 4 meters.
00:24
We're told that it has an electric field of 0 .54 .5.
00:30
Volts per meter.
00:33
And for gold, gold has a resistivity of 2 .44 times 10 to the negative 8 oms per meter.
00:45
So for the first part, we want to know what is the current carried by the wire.
00:51
And so we can use the equation.
00:52
Current density is equal to current divided by area.
00:58
We don't know current density, but we know, electrical field equation is equal to resistivity times current density.
01:06
And so we can solve for that where current density is the electrical field divided by resistivity.
01:12
So we can take this and plug it in our equation for j.
01:16
So we have electrical field divided by resistivity is equal to current divided by area.
01:22
Multiply both sides by area...