More little practice final exam things. But I'm not encouraging last-minute cramming. This is intended for people who've read everything and have already done everything I've already given. The topics:

 

1. Ratios of quantities in capacitors connected to each other. Pretty good practice document attached.

2. Electomagnetic Induction, Chapter 20, Algebraic Faraday's Law. Here's a core dump of a few more problems I have. It's not required to do all. Judge how much practice you need on the topic. Read the textbook examples on Faraday's Law. Also, Chapter 20 odd problems.

 

And HEY! Have you been to the site below yet? Have you been there many times?

 

 

Every year I ask this. Many students politely nod. And I can tell they're lying. I've told you all many times that it is full of problems. I shouldn't be the one who has to identify a breakdown like the following:

 

2018 Free Response Test #1: Electromagnetic Induction

2015 Free Response Test #4: Magnetostatics

2019 Free Response Test #1: Magnetism of some kind.

 

Do you find them on your own, take them as tests, and score your own with the Scoring Guidelines? I've told you to.

 

And not only that, skimming through, I noticed the electricity topic is well-represented on those tests I just referenced as well. I've said all I can.

Chapter 19 Practice Material for mastery:

 

The attachments can be broken into two major categories:

1) Various Practice Problem documents and Chapter 19 Problems off of the Study Guide. All but three of the files below are in this category.

2) Documents designed specifically to train for the hands-on part of the Magnetism test that will occur on January 9. To know what will happen, one has to be prepare. It cannot possibly be common sense or skills that derive from brilliance. The attached documents named "Interpreting The Meters Correctly To Know The Flow", "Ring Near Changing-Current Solenoid", and "Inducing A Current By Removing The Bar Magnet", taken in that order, are specifically for this purpose. When using these particular documents, if you're not making a mental picture of the physical objects and the field vectors at all times while reading them, they become a waste of time.

 

Note: HW progress checks I've done so far were not for mastery. They were just familiarity of certain basic things. I'll be grading mastery on January 9 with a quiz. Everything attached here is at the mastery level.

 

And finally, my spreadsheet infrastructure is all set up for January 7 for you to tell me what I need to know for grading for the two recent Experiments named "B Of A Bar Magnet As Measured By The Current Balance" and "Mass Of The Electron", both of which will earn you credit. If you have true, complete, realistic data that are legible and individually recorded (not in groups, there is no we) with clear units, then nothing can go wrong. None of this will be done by talking. I'll collect, I'll type, you'll work on something else while I do that.

Due Thursday Nov. 21:

 

New as of Monday 10/21: Look briefly at the two spreadsheets, which are the key to the Ideal Gas Law Experiment. The criteria for grading will be:

 

Absolute Zero in degrees Celsius accurately determined

N accurately determined

Was it on time? (green stamped)

Clarity of overall report (check-pluses were possible on this one)

Volume accurately reported, as determined from the circumference claimed - 2 sig figs required

 

 

The rest of what's below was the stuff that I posted on the afternoon of Thursday 10/17/19:

 

Due Monday 10/21 upon arrival - write-up on the Ideal Gas Law experiment

 

There is a prior posting that delivers the exact information for what is due in the write-up. I even communicated the rubric. It was posted prior to 10/17.

 

A portion of class population measured something crucial needed in meeting the 10/21 write-up goal. They did this on 10/17, because they read the rubric I posted, and they read it prior to 10/17. Another portion of class population were not aware that such a requirement existed*, and those people therefore did not measure a crucial piece of data required, and for them, the write-up is impossible to complete*. Therefore, I'll expect that a portion of the population will earn a late grade and another portion will have little trouble being on time*. But the following will not happen: there will be NO discussion of the missing piece of data in my classroom on 10/21/19 between 10:03 AM and 10:40 AM. Nobody will ask me questions centering around that missing that piece of data. If it's asked about verbally or talked about between students verbally, I won't accept the write-up at all. This is because it was a piece of data that was supposed to be taken care of during 10/17. I gave all period to do so, I put it clearly in writing, and I shouldn't have to read to the class what I put in writing in order for it to be a priority*. Options for those who don't have the piece of data as of 1:30 PM on Thursday 10/17:

 

1) It can be handled late for late credit, as long as it's measured without discussion.

2) It can measured on the A day of Friday, 10/18, and in that way, the deadline can still be met. This can be done on my classroom anytime between 7:50 AM and 12:30 PM, and takes about 30 seconds to measure this piece of data.

 

Why am I not saying what the piece of data is? Because it's clear if you read the document I already posted prior to 10/17. This document is called "Rubric Pre-announcement for PV = nRT Experiment". And I wrote on the board on 10/17: "Gas Exp write-up due Mon - tell me if online doesn't sufficiently define the objective." Again, some of the population were honest when they nodded and said, "Yeah, the online thing is good; I know what I'm doing." I know they were honest, because they went and measured the piece of data I'm talking about. It proves they read the thing and were prepared, because they knew you can't accomplish the objective without that last measurement bit. Others in the population weren't intellectually sound when they were polite in their passive non-responses to my writing, "Gas Exp write-up due Mon - tell me if online doesn't sufficiently define the objective." Passive non-responses are unacceptable. It means they didn't read what I posted. And I know they didn't read what I posted, because they didn't go and measure the last piece of data needed on 10/17. They'd have known this last piece of data was high priority if they had read the sheet.*

 

The solution for the number of molecules in the metal sphere will be graded individually for each student based on accuracy. Accuracy will be defined as a final answer that is consistent with the slope and intercept that each individual has already reported to me, and that I've already put in my correction spreadsheet. So you have to commit to the slopes and intercepts that have already been handed in and registered. Do not contradict these values in the rest of your write-up results. To be clear on what you have already registered with me, you may open the attached Excel spreadsheet.

 

The spreadsheet contains a blank column for the answer for your individual result for what absolute zero should be. To solve for it, one is locating the coordinates at the point on the best-fit line where gas molecules theoretically no longer exert force on the container holding them. In addition to the write-up being due on Monday, you will be telling me what your individual absolute zero value in degrees Celsius should theoretically be, as based on your data graph. I already know whose come closest, second closest, and third closest to the theory. The theory says the number should be -273 degrees Celsius, and everyone in this class is getting a value that is more negative than that. The winner is 7% away. A homework grade has already been earned by those having a good graph whose "p = mT + b" form made it possible for me to put values into the attached spreadsheet for both slope and b.

 

*You know, I was never intending to test the class to see if they read my "Rubric Pre-announcement for PV = nRT Experiment" document prior to 10/17. But it ended up turning into one of those little life tests. I figured it would go without saying that people would read that thing, come into class, and go right to measuring the new piece of data needed. Some did. They passed the unintentional test.

 

Well-defended conclusion for the number of molecules in the form of a lab report due Mon. 10/21. Data section has to be complete, trace back to the raw data, match what's already been submitted, and must include any new data info necessary in the solution of the conclusion.

Due Wed:

 

Finish reading Chapter 12, especially the part about Entropy and the 2nd Law of Thermodynamics.

Focus on Pages 399 through Page 413, and WE MUST MAKE A MAJOR CORRECTION IMMEDIATELY: Now, on October 21.

 

On Page 409, the textbook does not communicate something clearly. On that page, it is very important that you read about The Second Law Of Thermodynamics. In the reference to that law on that page, please replace the phrase "yet another" with the phrase "the most common." It's a big oversight on the part of your textbook to not highlight Page 409's 2nd Law as the most important version of the 2nd Law. The version on Page 405 (highlighted in beige) is of far lesser importance, because it is a far less universal statement.

 

Application: Calculate Q/T for two stages of the Stirling Cycle: For the stage from State 1 to State 2 and for the stage from State 3 to State 4. Each of these Q/T values will be called the Change in Entropy for the stage. Using 4 as the volume ratio, you should be getting a symbolic expression that can be reduced to a product involving N, k, and ln(4), where N is the number of molecules.

 

Note: The prior Stirling Cycle document is accurate. The key IS correct. It is calculated using the definition of U for diatomic gas. When molecules are diatomic, U = (5/2)nRT. The molecules in this device are those found in everyday air: hydrogen, oxygen, nitrogen; all of these are diatomic.

 

Checking of Entropy Change Answers: The stage from State 1 to State 2 will have an entropy change answer that can be reduced to a product involving N, k, and ln(4). When you do the stage from State 3 to State 4, see if you get an expression that involves the same symbols. One of these two answers will have to be negative while the other is positive. That means the two entropy changes will be of opposite sign from each other. When added together, should the overall entropy change be zero? See if you can relate this last question to your reading. Factor in the not-so-obvious fact below to help you.

 

Not-so-obvious fact: The heats involved from 2-to-3 and 4-to-1 ARE equal but opposite of each other. Will this mean their entropy changes are equal and opposite? It's hard to calculate, because neither stage runs at constant T. But I'm going to say yes if the stages are run with zero extra friction. This will correspond to the overall efficiency being as high as it can be. And this "As high as it can be number" will not be 100%. It will be (1 - m) times 100%.

 

And it will be easy to show that (1 - m) exactly matches the ideal Carnot efficiency.

 

Punchline: the ideal Carnot efficiency is the most efficient any engine can be, and it only happens when the entropy change of the cycle is _____.

 

Note: the only difference between the Carnot Cycle and the Stirling Cycle: In the Carnot Cycle, the vertical stages are replaced with adiabatic stages. In each of those, Q = 0. So for each adiabatic stage, change in S is just zero, as opposed to the Stirling Cycle, where we say that the two vertical stages add together so that their sum total change in S is zero, even though taken individually, one is positive while the other is negative. By the way, saying "zero" throughout this paragraph does not automatically fill in the blank of the last paragraph, because the blank of the last paragraph is referring to ALL FOUR stages added together.