00:02
So in this problem, so for the 9 -chrome wire, we know that the vrms equal 120 volts, and the power is 1 kilowatts, so we can determine the resistance of it.
00:21
So r equal to vrms squared divided by p.
00:28
So this gives you 14 .4 oms.
00:31
And in part b we want to know the lens of the wire so that we have this much we have this much of resistance so because the temperature at this moment t is 500 degrees and you can look up the value in a textbook and you can see that the ronauts for the nichrome equal 100 times 10 to the negative 8 oom meter so this value is for 20 degrees, okay? so we need to apply the relation, roanaut 1 plus alpha, so 500 degrees minus 20 degrees to obtain the new role for the nichrome, okay? and times l over s, so on the left side, this gives you the total resistance at temperature 500 degrees.
01:29
So this is equal to the total resistance, which is 14 .4 oms.
01:33
Okay, and you can also look up the value of alpha in your textbook, and alpha equal 0 .4 times 10 to the negative third per degrees.
01:45
Okay? so, you can solve for the l and obtain that l actually equal 60 .4 meters.
01:59
And part c, we want to know the initial power.
02:03
If we first switch on the this if it is first the switched on...