Topics in Physics

Spread the word, 8th period meets in 519 wednesday to hear about gravity waves

Thermo Notes

Note that the thermo notes uses R instead of kB. R is the molar gas constant and is simply kB x Avogadro's number. This makes sense because when we use R we use number of moles, n instead of number of molecules, N.

Honors Section 3

The electric power group and the magnets group have until the end of second period tomorrow to clean up their lab spaces or lose 10 points from their lab grade.

Corrected Thermo Worksheet

Here is a corrected version of the worksheet from Friday. Do it by tomorrow, Wednesday. By the way, thanks to Missy and Alyssa, [who did show up for the review session] for finding some of the errors, thus once again demonstrating their superiority to the thermo group.

http://h1.ripway.com/DrCherdack/Thermowsfor3-27%20r2.doc

Group Reports

Every student must produce a very brief report for a group meeting for each unit. If you did not meet you must still provide a report indicating this is the case, with a brief explanation of why you didn't. Honors classes need to have one for Units 7 through 9 by Friday plus at least one for the project. AP must have one for each of Units 9 through 13. AP must have one for 14 in by Monday and Honors must have one for Unit 10 in by monday

All Juniors Mandatory Assignment

Required assignment: an autobigraphy. You are to write about yourself, general personal history, likes dislikes, favorite subjects, any extracurricular courses you've taken, clubs, hobbies, sports, family, public or charitable service. This is due Thursday and once again IT IS REQUIRED.

Revised AP Reading

Sorry guys, the last post had the geometrical first and I decided we should do physical optics first this year, so please read this tonight. You can read the others Thursday or Friday night.

http://h1.ripway.com/DrCherdack/PhysicalOpticsSummary08.doc

AP Material on Light

We must press ahead very quickly.  Read the following Notes and Summary by Wednesday class time.

http://h1.ripway.com/DrCherdack/NotesonGeometricalOptics.doc

http://h1.ripway.com/DrCherdack/SummaryofGeoOpticsrev3-07.DOC

All Students and the rest of you as well

I just came form seeing our musical, Seussical. It was a tremendous performance. From the music to the singing to the dancing, to the lighting and the production as a whole, it was a tour de force. Many of the performances were of professional caliber. The pit musicians were faultless.

I urge you all to go see it.

Congratulations to everyone involved, you have every right to be proud of your accomplishments.

AP Unit 14 A Light

Here is the new schedule. Make sure you get the AP sheets you need Friday.


http://h1.ripway.com/DrCherdack/APUnit14Asched09.doc

http://h1.ripway.com/DrCherdack/Unit14Aproblemshr1.doc

Honors Assignments Firday and Monday

For tonight: study thermodynamic processes for reading type quiz tomorrow and do practice problems 2 and 3

For Monday: Complete worksheets from Friday in class and develop an equation for how much heat is transfered per second from the inside of a house wall to the outside. Consider the properties of the material all summed up in the thermal conductivity, kc (yeah, I know, another k) which has the units J/(sec m2 Kelvin); the thickness of the wall; the area of the wall; and the temperature difference between the inside and the outside. The units of kc should give you a good hint as to the rest of the equation.

Honors Thermo

Here is the link to the more thorough set of thermo notes referred to in your schedule.

http://h1.ripway.com/DrCherdack/NotesonThermoR5.doc

AP Labs

Things have gone from fair to terrible in the matter of lab reports. Only a double handful of you have turned in the magnetics lab. They better be waiting for me when I get back in Monday.

A description of what is required is available in a post of two days ago, in fact the last one prior to this.

AP Magnetics Lab

Guys although we did it as a class it is a lab and a formal, but not too long, report is required. Our goal was to test our equations for solenoid field, for force on a current with length L in a field, and our conjecture that we could use the solenoid field equation for the magnet if we used the force equation to find NI. If our calculation of the permanent magnet field strength was anywhere near the manufacturer's claim of .28 T our theory must be pretty good.

Labs should include a discussion ( not a proof) as to why our solenoid field equation and our force on a current equation make sense.

Honors Unit 10 Schedule

Here is the thermo schedule. Note we are well into it already.

http://h1.ripway.com/DrCherdack/HonUnit10Thermo09.doc

Labs

There has been a recent rash of lab reports coming in with near identical text for substantial portions of the report. This is not acceptable group effort. The consequence of this for the first offense is a zero for all but the original author of the words . I assume there will be no second offenses.

Those who truly collaborated on the wording RATHER THAN HAVING COPIED THE WORK OF OTHERS will have until Tuesday to submit an originally worded report. This last only applies to those who are in the same group. This Tuesday deadline does not depend on receiving the currrent lab back from me.

I HOPE TO NEVER HAVE TO POST ANYTHING LIKE THIS AGAIN.

All students

A reminder: Friday March 27, I will be attending a master class on particle physics with Charles Guo,  Avinash Hinogorani, James Belardo, Ryan Roelke, and Sarah Bottini [let meknow if I missed anyone].  I will not be at Ridge at all so  you can start planning the celebrations now.

Physics SAT II

I will hold 2 review sessions per week for the physics SAT II ( or subject test or whatever they call it now) starting the Tuesday after the AP exam, so see if you can hold off until the June date if you think the reviews will help you. Days will be chosen based on email requests received from you.

AP Practice problems

The three free response questions and the sample MC questions are due Monday. Use the info sheets for the MC and the info and equation sheets for the problems.

All students Thermo Notes

Here are some more notes on thermodynamics. The problems are due Monday for Honors classes, and recommended for AP as exercises, but are not required.

http://h1.ripway.com/DrCherdack/Thermonotes-prob-basic%20.doc

The correct AP Magnetics Schedule

Got it right this time.

Here is the schedule for our unit on magnetic fields and forces. MAKE SURE YOU READ THE NOTES ON MAGNETICS

http://h1.ripway.com/DrCherdack/AP%20Unit%2013%20Mag%20sched09.doc


http://h1.ripway.com/DrCherdack/Notes%20on%20magneticsR6.doc


http://h1.ripway.com/DrCherdack/Unit13Worksheet1.DOC

http://h1.ripway.com/DrCherdack/Unit13Worksheet2.doc

http://h1.ripway.com/DrCherdack/Unit13ProblemSheet.doc

Honors Class Wednesday 3/18

To facilitate our group research, we will meet in the computer lab 411 on Wednesday 3/18.

Honors Presentations

Group Presentations: You must explain things in a way that shows you have gained understanding and will help the rest of us do the same. Cut and paste recitations from web pages etc. are not acceptable. Minimum 20 minutes ( that's not 5 minutes plus 15 minutes for questions).

Thursday Thermo group on work in your cycle, just the main points for isothermal, adiabatic and isobaric expansions. Can discuss regenerative feedwater heating if you really understand it.

Friday Plamsa group drift, tansport and JXB = gradP

Monday (1) Magnet group, superconductivity, coil currents, coil features, conductors (materials) and forces. (2 - Sect 2 only) Electric power Group: Farraday induction, conceptual design of turbine : field coils, stator coils, exciter; number of field poles, number of stator coils (windings) size of coils, currents and volts, strength of magentic fields.

Tuesday (1) Heating group: description of ion source ( plasmatron(?), accelerator grid, neutralization chamber; beam dump. Provide design info such as size, voltage, energy, operating pressure. Use ITER as a basis, but you must understand what you are talking about. (2 - Sect 3 only) Electric Power group see above.

Honors Assignment for Monday Night 3/16

Due tomorrow gas expands at constant pressure from V1 = 1 m3 to V2 = 2 m3 T1 =500K P1 =P2 = 5 atmospheres ( you must convert to Pa of course).

Find T2; Find Q into gas use Qin = Work done by gas + N c DT;

use KE of average particle = 3/2 kboltzmann T .

You obviously need to find N and you can use a relationship we have already developed to do that.

P1 =P2

Honors Kinetic Molecular Theory and problems

Here are notes on where pressure comes from in gases and problems due Monday.

Note that for plasmas, the nuclei and the electrons are the particles, instead of molecules, as in a gas.

http://h1.ripway.com/DrCherdack/Notes%20on%20Kinetic%20Molecula.doc


http://h1.ripway.com/DrCherdack/Gas%20and%20Plasma%20Problems%20%20.doc

Honors Buoyancy

I noticed that many of you used an equation that said delta mg = FB. Since it was incorrect in the quiz problem, it took me a while to figure out where this came from and then I realized it came directly from our lab. The reason it is incorrect in the problem is that in the problem the scale is holding the object up ( teh object is hanging from the scale) and so the force the scale has to exert in the problem is REDUCED by the bouyant force pushing up and now the scale and FB are both togther countering Mobject g. i.e. FB + Fscale = Mg.

In our lab, the string was holding the object up and when we place the object in the beaker the fluid pushed up reducing the force the string had to apply. However the scale reading INCREASED because since the water pushed up with FB there was a force from the object DOWN on the water = FB so in the lab the final scale reading equal weight of water and beaker + FB, and so FB = deltaMg in our lab.

Honors Homework

Tomorrow be prepared with specific questions you need answered to make the next step of progress in your design. So review your resources and determine what you need from me to proceed.

AP Homework

You have several loop problems tonight. Kirchoff's Junction rule says that the currents into a junction(the meeting of two or more wires) must equal the currents out. [otherwise charge would accumulate or deplet a tthe junction]

Kirchoff's Loop rule says that total voltage gained ( say from a battery or other source) minus voltage drop through resistors, etc. ( and backwards batteries) =0 around any complete loop.

Try your best

AP worksheet 1 r1

This has at least one correction I made last year and forgot to post. The one Iam sure about is on question 9 overall R

http://h1.ripway.com/DrCherdack/Unit%2012%20Worksheet%201r1.doc

Electric Potential

Many students still think of work as only being found from F dot distance. This view ,while largely correct is not particularly useful when F varies over the distance, especially when this variation is not linear the way it is with a spring ( here F = k delta x so even though k varies it is easy to calculate the work). The best way to approach work with a non constant force is to remember that work changes energy. For example, if you are moving a charge QT without large changes in KE the work = delta PE = QT x delta V.

Some students are still using the potential created by a test charge in calculating the potential the test charge feels. Don't do this, see earlier post on subject.

Honors fluid practice problem

Note that in problem 3 the number in parentheses is the the Pa per atmosphere. The pressure is 100 time this, or 1.01 E7

AP Errors on Unit 11 Practice Problems

Question 2(a) should ask for the change in KE

Questions 2 d should read "previous results". Answer to Question 2 (d) should read no change in velocity; field is 1/2 as great as original

Honors MHD Problems

We are still a few days from doing those so keep an eye on the blog to egt them when we are ready for them.

Grade rehabilitation

Those of you attending review sessions and turning in homework in the hopes of the last two periods being weighted more heavily than the first two:

1. The deal is 95% on homework for each of quarters 3 and 4. I am not seeing that in many cases

2. You must have attended 80% of the review sessions. If sports interfere, being 1/2 hour late for practice for seeking extra help should not lead to any reprisals from your coach. Let me know immediately if this is not the case.

3. If enough of you need to switch times, I am open to suggestions; but you must work it out amongst yourselves and present a plan to me.

Grades

I posted cumulative lab grades, homework grades, and test grades, for all materials graded as of last Thursday.

The total grade is a crude indicator of your class grade. If you have received a comment about labs or a grade below 80 in lab you should be seeing me.

I will be glad to discuss any other issues with you outside of class hours.

AP Currents Schedule

Here is the schedule etc for AP Unit 12 Currents

http://h1.ripway.com/DrCherdack/AP%20Unit%2012Currents%20Sched09.doc

http://h1.ripway.com/DrCherdack/Unit12Worksheet1.doc

http://h1.ripway.com/DrCherdack/Unit12Worksheet2kirchhoff.doc

http://h1.ripway.com/DrCherdack/Unit12ProblemSheet.doc

All Students READ THIS

One of the major problems students ( and the rest of you) seem to have in electrostatics and magnetics problems is distinguishing fields established by sources and the fields the test charges and test currents create. A charged particle exerts no force on itself.


The question determines which charges or currents are viewed as source(s) and whch as test(s).

The force comes from the field produced by other ( source charges). For example, if I tell you an electron is placed in a field of 300 N/C and ask you for the force on the electron, acceleration of the electron, etc., you have no business fidng the field created by that electron. If you multiply a charge by the field that same charge creates you are finding the force of the charge on itself, and doing it incorrectly since the field right a at charge must be infinite(1/ zero squared, since the ditance between the charge and itself is zero). [ Note that with charge distributions an individual charge can feel a force from the rest of the charges in the distribution but there is no net force on the entire distribution from itself or any single charge from that charge itself.]

The same applies to currents, source currents create magnetic fields and test charges or test currents experience the field and feel a force.


[A wire can exert force on itself if it is in a coil or other curved shape, BUT NO NET FORCE ( THE LEFT SIDE CAN PUSH OR PULL THE RIGHT SIDE BUT THE RIGHT SIDE PULLS THE LEFT SIDE JUST AS HARD IN THE OPPOSITE DIRECTION.]

Dielectrics in Capacitors

Your capacitor equation has a funny k, kappa, in it .

Kappa = (the epsilon for the actual dielectric in the capacitor)/( epsilon zero). Unless you are given the kappa or the actual epsilon, assume epsilon = epsilon zero.

AP Currents assignment

Make sure read the Notes on Currents posted with the Unit 11 Schedule

AP Assignment

Because of HSPAs and snow the chapt 17 assignment from Thursday is due Monday. Make sure to study for the test on electric potential, energy, and capacitance.

Notes on Electric Potential

Here are some notes on specific items concerning electric potential. They are not meant as a thorough discussion of the subject but they are useful.

http://h1.ripway.com/DrCherdack/Notes%20on%20potential.doc

Irons Lecture on magnets and Superconductors

Great Lecture this Saturday at Rutgers. See post from last month ( Feb) or me for details.

AP Static Electricity Lab

You were warned to read the questions and that Observations D-1 and D-2 are not the same as Procedure D-1 and D-2. However, many of you answered the question (#6) referring to the procedure steps rather than the observations.

Reading questions and listening to instructions are important skills and increase the chances of you supplying the desired information.

In the lab, only the electrons were mobile, and then only a very tiny fraction of the total electron population. The total electron population comprises many tens of thousands of Coulombs, whereas the net charges were probably fractions of a micro ( 1E-6) Coulomb.

AP Resonance Lab

One of the questions asked what would happen if the temperature rose 5 deg C. Wavespeed would increase is not a satisfactory answer. lambda would increase is not a satisfactory answer. L would increase is not a satisfactory answer. They gave you an equation for c, they gave you a number of deg temperature increase. A satisfactory answer comprises recalculated c, lambda, and L, and nothing less.

You must stop doing the minimum and not insist on having detailed and explicit instructions before doing something. The world is not a fifth grade workbook telling you exactly what to do. If you are given enough information to find something out, do it, even if it requires multiple steps.

Honors Fluids Schedule

Here is your schedule for the unit on Fluids

http://h1.ripway.com/DrCherdack/HonUnit9Fluids09.doc

http://h1.ripway.com/DrCherdack/NotesonFluidDynamics.doc

http://h1.ripway.com/DrCherdack/ReviewShFluidDynamics.doc