00:01
So let's say we have a copper wire that has a diameter of 0 .284 centimeters.
00:07
So really quickly, that's just a radius of 0 .142 centimeters.
00:13
And copper has a resistivity of 1 .68 times 10 to the negative 8 oom meters.
00:25
And we're told that this wire is used to connect a set of applying.
00:30
At 120 volts and they draw 1850 watts of power so our voltage here is 120 volts and so the first question asked what power is wasted in 27 meters of wire so let's take the length of our wire to be 27 meters so the the current here is just going to be the power divided by the voltage so the current feeding these applying is 1850 watts divided by 120 volts, excuse me, so this is 15 .42 amps.
01:14
That'll be important because the power wasted by the resistor is just gonna be i squared, or sorry, by the wire is i squared times r.
01:22
And r is gonna be the resistivity of copper times the length of the wire divided by the cross -sectional area.
01:30
All right, so we can plug in these numbers.
01:32
This is 15 .42.
01:35
Amps squared times 1 .68 times 10 to the negative 8th ome meters...