00:01
We are given that r is 100 oms, l is 2 henry, c is 5 times 10 to the negative 6 power, ferid.
00:27
The resonant frequency, omega 0, which is 2 pi f sub 0 is the square root of 1 over lc so f sub 0 is 1 over 2 pi square root of 1 over lc put that in a calculator l is 2 c is 5 times 10 to the negative 6th power, so that gives me 50 hertz.
01:19
Let's look at part b.
01:28
So v -0 is 100 volts.
01:40
The frequency is the resonant frequency.
01:44
So i'm going to write 2 pi times 50 hertz.
01:56
So i'm not going to write the hertz.
01:59
Actually, i'm not going to write any of that, because 2 times 50 is 100.
02:07
So i'm just going to write 100 pi, radiance per second.
02:16
So we're trying to figure out the power.
02:20
So power average is 1⁄2 i .5.
02:31
V .0.
02:33
Cosine theta.
02:43
Okay, to figure this out, i'm going to have to get the impedance r squared plus omega -l minus 1 over omega -c squared.
02:58
Let me put that in a calculator.
03:03
Where root of r squared, r is 100.
03:13
Plus.
03:18
Wait a minute.
03:19
I'm not thinking ahead enough.
03:21
If it's at its resonance frequency, then the resistance is just r, which is 100 oms.
03:31
I wasn't thinking that it's at its resident frequency.
03:34
So let's forget about that.
03:36
That would have worked, but that would have taken a lot longer.
03:40
Okay, the power output from the source.
03:44
Well, the power, we can get rid of the, this cosine of theta now, it's just going to be one -half i -0, v -0.
04:00
But we know that v -0 equals i -0 -r.
04:13
And so i -sub -0 is v -0 over r.
04:20
So we can substitute this up here, one -half v -0.
04:26
Squared over r.
04:29
So i can put that into a calculator...