Hi ladies and gentlemens, here is Kenny who doesn't know Physics at all but writes this blog for you. How ridiculous!? However it is my duty~~~
**OK~~ Let's start with our quiz. The hardest quiz I ever had in this week~~~It is a capacitor problem that we used to find potential different in anytime and anywhere. (2 charge problems are exception.)
a.) Compute the charge on the capacitor just before the switch is thrown from position 2 back to position 1.
Start with Q = CE (1 - e^(-t/RC)), where RC = T = 1.3E-5 * 960 = 0.01248sec
We have E = 18V, C= 1.3E-5, t = 10ms = 0.01 sec and RC = 0.01248. So we can find V!!!!!
Q = (1.3E-5)(18)(1 - e^(-0.01/0.01248) = 1.29*10^-4 C
Then we did c. first rather than b. , because c is easier!!!
c.) Compute the voltage drops across the capacitor at the instant described in Part A.
Pull out you equation sheet!!! V = Vo(1-e^(-t/RC)), the best way to do this problem~~!!
Vo = 18V t = 0.01sec RC = 0.01248
V = 18(1-e^(-0.01/0.01248)) = 9.92V~~~~ That's it~~~!!!
Go back to b.
b.) Compute the voltage drops across the resistor at the instant described in Part A.
Evaluate this problem as Kirchhoff's rule problem.
Vo - Vc -IR = 0
18V - 9.92V = IR - 8.02V
d) Compute the voltage drops across the resistor just after the switch is thrown from position 2 back to 1
In this problem, battery is taking out from the circult, the capacitor becomes the power source!!
Vc - IR = 0 (Kifchhoff's rule again!!)
9.92 = IR ~~~~~!!!
Question e is equal to question d!! Did anyone do it in the quiz?? I hope not !!!!!
f.) Compute the voltage drops across the capacitor just after the switch is thrown from position 2 back to position 1.
This time we have V = Voe^(-t/RC)
g.) Compute the charge on the capacitor 10.0 ms after the switch is thrown from the position 2 backe to position1.
We have a faith from PMason to solve this, which is:
Q =CV
muti C for both sides on the equation at part h.
CV = CVoe^(-t/RC)
q = Q0 e^(-t/RC)
Here, I need to apologize with problem g & f, I missed the final answer for both question. Can anyone help me out, upload the answer by a comment!? Thank alot and I am so sorry......
How did you do!? Well done!? Bless you and hope PMason gives everybody an A~~~~~
Forget about the old stuff~~~ That is a new chapter coming in, and which is magnetic field!!!
We started with playing magnets!! As we saw that they attract and repel each other in particular way, we noticed that magnet has two poles - North pole and South pole. (What a big new!!! ...... for an elementary school child =@=")
**Then, we discussed some characteristics of magnets and magnetic field.
1. North geographic pole is a south magnetic pole. Oppositely, South geographic pole is a north magnetic pole. (WHAT??@@??)
Yeah, that surprise me also. North is not north?? south is not south?? It may causes you seconds to understand it. Let's take a look with a compass, it helps. The south needle attract with the north magnetic pole in the south pole. Therefore the south needle always point towards south. It can also apply on north needle. It is clear?? @@??
2. Ways to dismagnet a magnet
It should be an extra info. - We can dismagnet magnets by banging one to another, or put them into fire . (High temperature disorders the orientation of the magnetic field inside the magnets.
3. Orientation determination (Magnet)
Just like what I described above in 1.
4. Destory of a magnet
Only one point - If you cut a magnet in half, the origial south pole and north pole are keeping in same magnetic pole. New poles are created in other ends of the magnetic.
N == S ----Cut it half----> N=S N=S
5. Reorientation
Do you remeber how PMason put a line of staple on the huge magnet that Chung plays alot!? The staple gets magnetic field for awhile. It shows that metal can reoriented by touching another magnet!!!
**The following is the main part of this meeting!!! Magnetic Field.
PMason put some metal powder around a magnet. We saw a particular pattern formed! That pumpkin liked shape is the visual shape of magnetic field.
Actually Magnetic Field (B - SI unit: Tesla & Gauss) is pretty much like other Field. It also has flux. We know Electric flux is equal to the intergral of E*dA. Magnetic flux is equal to the intergral of B*dA. The main different of Magnetic flux from Electric flux is the net magnetic flux in a closed three dimensional surface. Because there are no magnetic monopoles as pole should be in pair. So the net magnetic flux coming out of a close 3-D surface is equal to ZERO!!!!
Lastly, we played with an oscilloscope. PMason described the structure of the oscillosocope. The visual light from the oscilloscope can easily influenced by changing the charges of the parallel plates inside the oscilloscope. It is hard to explain all the variables. However we must remeber, It visualized Britney Spears Voice !!!!!!
............Oh my God ~~~ I wrote so much stuff. In order to make this blog complete. I want to add something at the end. "Where I have words on my Lab Notebook!!" I hope it helps everyone to know which exercise(s) we have done for today's lecture.
Where I have words on my Lab Notebook:
11.4.1 b.c.d
11.5.1 a
11.6 all
It is time to play PS3 ~~~ see ya~~~~
Kenny@Mason4B
