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.
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