Monday March 30, 2009.

For all of our hard work Mason has granted us a day off from class. Even though it's on account of jury duty we still thank him for a four day weekend. The timing seems really convenient but we won't poke holes at it. Thank you professor Mason!

We should be covering Gauss's law (Chapter 22) on Wednesday for those who want to get ahead.

Answers to my practice test

Answers for practice Celebration

Day 8 March 18

Today we did section 6.1-6.5 on our handout. For the first part of class we started off by solving some problems on the motion of an electron in a uniform electric field. we learned how an electric field affects the motion of an electron with an initial velocity and that E-field causes the deflection of the electron in the oposite direction of E. we did some calculations on our white boards to prove that the deflection is proportional to voltage.. and by using these equations:
F=ma
F=qV/d
and 2D- kinematics equations for the trajectory of the electron we were able to solve for d, and we realized that the deflection is proportional to Voltage(the higher the voltage the greater the deflection). we needed this information in order to understand the second part of class, which delt with function Generators and Oscilloscopes.
For the second part of class we played around with a function Generator, also called (wave generator) which is a device that can produce different voltages in a regular pattern. we connected a speaker to the wave Generator and we played around with different dials and bottons on it and we noticed the sound changes: 1) changing the frequency changes the pitch of the sound. 2) changing(increasing) the amplitude makes the sound louder . 3) changing the function(sine, triangle or square) changes the timbre of the sound coming out of the speaker. After that we learned how to use an Oscilloscope and we connected in to the function Generator and noticed how changing the frequency and amplitude changes the graph(motion of electron)displayed on the screen of the Oscilloscope. we also learned how to calculate the period by just looking at the graph.
for the last part of lab we built capacitive filter cicuits on our breadbord, and we conected it to the Oscilloscope and the function generator. then we collected data for the changes in amplitude and voltage when we change the input frequency. then we graphed the data we got using loger-pro. and we noticed the constant votage drop in the first circuit(capacitor and resister), and the constant voltage in the second circuit(two resisters).
GOOD LUCK ON THE EXAM!
O MY BAD, (CELEBRATION OF KNOWLEDGE!)

Practice test for celebration 1

This is a practice test that I made up. There was no input from Prof Mason on any of these questions, but I thought these were fairly challenging and would pose a good exercise. Prof Mason said he would be handing out his practice celebration on Monday.

Peter's Practice Test

The answers for my practice test will be posted Monday night. I will attempt to have the answers for Masons up on Tuesday night or Wednesday morning. Good luck with studying =)

Edit** For problem one, there is a positive test charge at the point where you need to find the force and electric field.
Problem two, it should be surface charge, not linear

Day 6 March 11, 2009

The first thing we did in the class was a quiz. The quiz is about using the Kirchhoff's Rules to find current in the circuit. Then using the current to find the voltage and the power to compute the total power.

Generally, we use the sum of current and voltage in a loop are both equal to zero to find the current. First, The junction rule I1=I2+I3 will setup the first formula, and the loop rule will create the other two formulas. Then, we can do some algebra for the unknowns in the formulas to find the current. After that, V = IR can be used to find the voltage by current and resistant. Finally, use P = IV to get the power of each resistor, and add them up to get the total power.

I did the questions wrongly, but I found my mistakes soon. All loops have to in the SAME direction. It was a good quiz because I even did not find I was doing something wrong in the homework!


The second part in class was slightly different with the class. We were learning something which is not in the book! The robot project was started! Before touching the hardware, we had to learn some theory for that.

What we learned in this part was the protocol for the devices to communicate. We learn how it works. It translate ASCII code(American Standard Code for Information Interchange), which is commonly used in computer system to represent characters and to some digital signals. The character in ASCII code first translates to 0 and 1, then it reverses the order of the code then translates to positive voltage for 1 and positive voltage for 0.


The third part was doing some labs. We use a voltage divider, a potentiometer to build a bridge circuit to measure the temperature. We take the voltage in the freezing and melting point, which are already known as 100 and 0 degree Celsius, to calculate the room and the body temperature. From the result, we will get a line which show that they are in linear function.

An interesting thing in the lab is that we found this device is really sensitive. It could even catch the temperature change caused by our human body moved away for a few centimeters!

Solving circuits with matrices

Here are the instructions for solving simultaneous equations with your calculator. Note, these directions are for the TI 83 + only. If you have a different model, your procedures will be different.

http://docs.google.com/fileview?id=F.f9c99189-1d8a-4dce-8ad0-9bd68b62ef01

Hmm

Better Be Right Or Your Great Big Venture Goes West

Here's one that's PC, kosher, etc.

SI times are set for the rest of the semester. I have no intention of changing them anymore. Hope to see all there!

Day 5 Physics 4B March 9, 2009

Really long recap:

Some important announcements were made before class today. First of all Peter set a new SI session date. His new session will be on Friday from 10:00am-12:00pm. I cannot confirm this as a static date/time so you’ll have to prod him for more information whether it will change or not. His other sessions that are an hour before class will remain the same for all your last minute homework needs. Incase you didn’t know an hour before class is 11:00am-12:00pm (class starts at 12:00pm). That brings me to the next announcement. BE ON TIME! The more you guys are late the more often we have quizzes. I don’t know whose idea it was to reward the people that are on time with quizzes but something seems quite off with the logic.

In class today was more of a problem solving day with some hands on but not quite as much as the previous week. We covered sections 4.5 to 4.13.1e in the packet in the seamlessly short 220 minutes we have together; although most of us didn’t get even close to part E so we should be continuing it on Wednesday. The first lab we worked on involved comparing which resistor gets hotter (spoiler: the one that causes more pain gets hotter). The purpose of this was to see whether more or less resistance causes more or less heat respectively. The answers may not surprise you. To prove this Mason hypothesized it would be less painful to light a 5 ohm resistor on fire than to hold it. After a lot of waiting and smoke the flames never emerged and we were all disappointed with Masons promises not delivered. With the lesson of not lighting resistors on fire learned , or in my case “try this at home until we get results”, we next learned how to identify the resistance of a resistor by the color coding on the resistor itself. There are some easy rhymes to remember the BBROWGBVGW that can be found with Google but posting there here might be frowned upon for not being PC (about 80% contain rape for red and it only goes downhill from there). After practicing the codes for a while we moved onto the meat of the day; Resistors in series and parallel calculations by either brute force or Kirchoffs Law. I will make the lessons learned from these at the end of the blog in an easy access location. This part of the day dragged on endlessly for what seemed like eleventeen hours. But when it was all said and done I shall, along with many others, be harassing Peter for help on Friday about Kirchoffs law (since when was a law ever easy to understand). In our curiosity about the 5 ohm resistor that was “lit on fire” we decided to test the change in its resistance after being exposed to high heat. There was a minimal change in resistance as recorded by the multimeter. Those lil’ guys are Tonka tough.

Notes:

One of the more interesting things we did as a quick refresher was we wrote V, I, Resistance and P in terms of SI units. They turned out to be:

-V = ( Kg * m^2 ) / ( s^2 * C )

-I = C / s

-Resistance = ( Kg * m^2 ) / s

-P = ( Kg * m^2 ) / s^3

Some handy notes for series/parallel resistors were:

-In series the voltages will add together but the currents will always be the same.

-In parallel the voltages will always be the same but the currents will add together.

-Add the resistances together for total sum in a series: R1+R2+R# =Rtotal

-For parallel multiply the resistance of each resistor then divide by the sum of all the resistors: (R1*R2*R#)/(R1+R2+R#)=Rtotal

Kirchoffs Law:

-The algebraic sum of currents into any junction must be equal to zero.

-The algebraic sum of the potential differences will also total out to zero.

-As long as proper signs are used Algebra or matrices can be used to solve these problems relatively easily.

-Page 888 of the book has more details on this (what a conveniently easy number to remember).

Fun things:

-On March 9 1934 Yuri Gagorin was born. He was the first man to go into space. (closest fun fact related to Physics I could find for March 9). On the plus side if you look at his picture on Wikipedia he has more medals than Michael Phelps.

-As an apology for such a sad fun fact here’s an awesome Physics related game to play when you’re bored… but not bored in class… unless you’re Mason… or Peter…

http://www.fantasticcontraption.com

Whenever you finish a level go look at some of the other ones people have created. They make you feel really bad for not being that clever.

In summary:

Read sections 26.1 and 26.2 of the book as well as 4.8 in the packet to recap everything we did today.

**no Peters were harmed during the learning of this class... sadly.**

• Day 4 03/04/09
  Today is another exciting day at our Physics4B class. At the beginning of the class, we took our first quiz of the semester. I was a little bit nervous at the first, but once I look at the quiz, it is exactly the same as our homework, and we also can use the notes from homework. I am very happy that I know I get a 10/10 on the quiz, and it makes my day.
• During the class, we did several experiments about series and parallel circuits. In the first experiment, we found out that in a series circuit both V and I are the same, but in a parallel circuit that the parallel bulb split the current. Then, we did an experiment to find out the resistance. We set up a circuit and use the V meter and I meter to find out both V and I of the resister, then use logger pro to get the resistance. I like today’s experiments and we learn a lot of things from them.
• At the end, we had the change to use the multi-meter, it is pretty cool because you can measure a ton of things from it. Professor Mason also told us the multi-meter only measure the V from the object that makes it more awesome. Anyways, the best thing of today is I did well on the quiz, and the experiments are pretty good. Look forward of Monday’s class, by the way this weekend we got change the time one hour early, it means we have an hour less of sleep. Hope to see all of ur guys on Monday, good luck on all the classes!!!!!!!!!!

Day 3 3/2/09

well today for the first time in physics, I saw the light at the end of the tunnel! literally..

Before we played with our light bulbs and batteries, we continued in the packet from 2.9 to 3.8.
finishing up the subject of potential energy. That brought us in the topic of Equipotential surfaces. A big fancy word for a very simple concept. dont freak out with all the lines, just remember the equipotential lines always go perpendicular to the direction of the electric field lines.

The best news all day was to cross out section 2.11. we're not doing it, ever. (songs of rejoice)

Now after all the hard math and complicated integrals we got to simplify our mines and connect the dots. or the circuit. playing with completing circuits to power up the light bulb, or 3 light bulbs, and drawing the circuit diagrams for them. learning the ideas and concepts of current, resistence, and voltage. were all basic in concept, but all vital for any further process.

But if i could get you to remember one thing from this whole day, I would have to say, GET TO CLASS ON TIME!! Prof Mason has been nice enough to grace us with no quizzes but because of the lack of bodies there at 12 he is threatening us. so for the sake of me you and the guy next to you, please get there on time so we can avoid these annoying quizzes!

see you all wednesday, at 12 noon!