Notes on Fluids

Here is a better set of fluids notes
NotesonFluidDynamics.doc

Revised Astrophysics Program at Rutgers

[ I have included the address for another web page that explains the program a bit better] We are looking for a few good students interested in learning about x ray astronomy in cooperation with the Rutgers Astrophysics program. It involves attending a four week summer course and then doing research and attending monthly meetings during the school year. It is a chance to create your own research and learn how to download and manipulate the same data astrophysicists use in the course of their research. Deadlines are coming up very soon so go right to http://www.physics.rutgers.edu/asi/asi_general.html and see if you would be interested. If so go to http://www.physics.rutgers.edu/asi/asi_student.html and begin the application process and then contact me or Mr. Gilmore immediately.

Honors Projects

Projects ARE REQUIRED for the 4th quarter. They should be something you can build, demonstrate AND EXPLAIN. Proposals for Honors Physics projects are due Monday 4/30. Proposals should be clear as to what you plan to create and how it works.

Subjects which are acceptable include:

fluids, sound, electricity and magnetism, light and optics. ( Newtownian mechanics and rotational motion are not acceptable)

Ideas include motors, speakers, generators, musical instruments, telescopes and microscopes, micrphones, spotlights, fluid systems demonstrating Bernoulli's principle.

Good Luck

Revised High School Astrophysics Research Program at Rutgers

We are looking for a few good students interested in learning about x ray astronomy in cooperation with the Rutgers Astrophysics program. It involves attending a four week summer course and then doing research and attending monthly meetings during the school year. It is a chance to create your own research and learn how to download and manipulate the same data astrophysicists use in the course of their research. Deadlines are coming up very soon so go right to http://www.physics.rutgers.edu/asi/asi_general.html and see if you would be interested. If so go to http://www.physics.rutgers.edu/asi/asi_student.html and begin the application process and then contact me or Mr. Gilmore immediately.

AP MC and Free Response

I will probably post some solutions near the end of the vacation so keep checking the blog.

Reminder The 1999 and 200 Free Resp and the MC #1 are for practice. The other Free response and MC #1 are a real take home test.

Compton Scattering

Compton scattering results from photons colliding with electrons. In these reactions the photon loses momemntum thus its wavelength increases.

lambda post collision - lambda original = [h/ (mass of electron x c)] [1-cos(theta between ooriginal direction and final direction of photon)]. This angle is usually called phi but not in your text.

Fluids Notes for ALL and Honors Schedule ,Rev Sht

Here are notes on fluids for everyone (AP should have hard copies already), and a schedule for honors and a review sheet.
NotesonFluidDynamics.doc

HonorsUnit13Fluids07.doc
ReviewShFluidDynamics.doc

AP Practice

Try to get throught the entire AP Test Package your received today by Monday. I would like to go over the most troubling problems with you on Monday.

Enjoy the weekend.

Honors Assignment

Your assignment for the weekend is to write a report on the magnet strength measuring device development lab we did on Thursday. I strongly suggest you develop this lab report in groups, but each report must be written in your own words. It is due Monday

Key ideas: Goal is to find B of the permanent magnet.
The force was measured by using a balance to get readings with and without the magnet near the solenoid ( coil). so Fmagnet on solenoid = F solenoid on magnet= (Mwith-Mw/o) x g

Magnetic Field generated by solenoid is Bsol = mu0 x I solenoid x N turns (500 in our case)/ solenoid height ).

F solenoid on magnet= L IPermMag x B sol.

Where IPermMag is the equivalent current in permanent magnet and L is the perimeter of the permanent magnet.

Then B PermMag = mu0 IPermMag/height of Perm Mag

Enjoy your weekend

Modern Physics for AP

Here are the notes on Modern Physics for you to read this weekend.

ModernPhysicsReview.doc

ModernPhysicsSummary.doc

AppendicesRevModPhys.doc

Perhaps we'll have a reading quiz on Monday

AP Light Problem Sheet

Here is the link for the Unit 14 B problem Sheet

Unit14Aproblemsheet.doc
Ignore the 14 A in the title, I used to teach Physical Optics first.

Honors Magnetics practice problems

Here is the link to the schedule with the parctice problems attached. See you tomorrow.

HonorsUnit12Magnetics.DOC

Currents and Circuits, Circuits Lab

Many of you still seem to not understand that currents arise when a potential difference (i.e. voltage drop) is placed across an element. This creates a field which makes electrons have an average velocity in the direction opposite the field ( because thay have a NEGATIVE charge). Tis flow of electrons is the current. The current through an element depends on the voltage drop across that element; it is not some magic fixed number which is always the same. The total current depends on the overall conductance [or 1/ (Rtotal) ] x Von the whole circuit.

Many of you also do not seem to understand that the voltage source provided V Joules per Coulomb and that the joules per coulomb ( i.e. volts) lost by a charge going around the circuit must add up to the Voltage gained from the voltage source.

ALSO SEE 2 previous posts 1 On Bulbs and 1 On Circuits

Grades and Mandatory Study Groups

Study Group Meetings are Mandatory for 3rd Quarter for Honors and AP.
The rules are
Honors: no meetings no grade for quarter. One meeting lose 2.5 points. 2 meetings lose no points.

AP: fewer than 3 meetings no grade; fewer than 4 meetings lose 5 points.

You have until Tues AM to fix this. Each person must submit a report for each meeting covering time/date, place, subjects discussed.

You must meet outside class hours. NO faking reports .



Here are what my records show for those with fewer than the required meetings by Student ID:
AP Period 1 3 meetings: 80873, 85763, 201269, 201972, 2 meetings: 82845 all others 4 or more
AP Period 6 3 meetings: 300484, 82360 2 meetings: 81130, 80320
Honors Period 3 0 meetings: 80178, 204134, 202381, 201256, 80930, 84400.
Honors Period 3 1 meeting: 80845, 200841, 80911, 202431, 85194, 81700, 201112, 85306, 81766, 83290

Honors Period 8 All have 2 or more, nice going.

AP and Honors: Circuits with Bulbs

I have uploaded a solution for a problem essentially identical to the one I gave honors as their circuits lab and also similar to the questions in the AP circuits lab. Honors students please note that here I have used bulbs A and B as 3 W and C as 6 W. These are all the rated power when there is 12 V across the bulb. If the voltage across bulb A, VA, is less than 12 the power used by bulb A will be reduced.

Many of you in AP and Honors still do not have a clear understanding of the fact that current is caused by a voltage difference (or voltage drop) across an element. If you remove that element its current no longer exists. Sometimes some current will increase elsewhere in the circuit, but this is because voltage across that part of the circuit has increased. Batteries produce nearly fixed voltages. The current flowing to and from the battery varies inversely with the circuit resistance. Removing part of a parallel branch removes a number of electrons that were subject to fields in that part of the circuit and thus reduces the current in the circuit. Another way of saying this is removing a parallel element increase the circuit resistance (decreases the circuit conductance).


Here is the solution set

BulbCircuitSolns.PDF

Notes on Magnetics for Honors (and AP )

Here are some notes on Magnetics. Down load and read them. AP students should already have done this!

NotesonmagneticsR4.doc

Spherical Mirrors Derivations

Here is a derivation of the fact that f=R/2. It is the most direct one and one of the simplest ones I could think of.

Derivoffforsphmirr.doc

Here is one for the equation relating focal length, distances, and image sizes. It is slightly different from the one in the notes.

Derivlenslawsphmirr.doc

Circuits/currents Labs for AP and Honors

This is relevant to both AP and honors classes. I have reviewed several labs from my AP classes and I found nearly everyone still fails to understand what causes currents. We began this subject with a discussion of how a current through a conducting element or object RESULTS from a field through it. The field through a conducting element is directly related to the voltage across it. Thus the current through an element depends on the voltage across the element and the property of the element known as its conductance, or
I = V x conductance or more commonly

I= V/resistance where resistance ,R , = 1/ conductance.

Thus if you hook up a battery to three bulbs, R1, R2, and R3 in parallel and then disconnect R1, the total current through the battery drops but the current through R2, which is due to the voltage across R2, does not drop because the voltage across it did not drop and its resistance did not change. [ If they were in parallel, the current through R1 never went through R2 or R3.] Yes the total current did drop but not the currents in each of the two remaining bulbs. The battery produces less current but about the same voltage. If R2 and R3 are in parallel with each other and then the pair is in series with R1, if R3 is disconnected, less current will flow through R1 so V1 across R1 must have decreased and V2 across R2 will increase because V1 + V2 still must equal Vtotal from the battery as before. Thus R2 will have more current through it, more voltage across it and produce more power. The reverse will be true for R1.

In fact when one in three parallel bulbs goes out, slightly more voltage is available to the remaining bulbs because the current flowing through the battery and thus through the small internal resistance in the battery is lower, reducing the internal voltage drop in the battery. This means the battery output voltage will go up slightly. AP students should have noticed that the voltage in part A of the lab with its small total current was higher tan in Part B, with its larger total current. Honors students should also become aware of this small effect when you find the drop in R internal for the series (low current lower V drop across Rinternal) and parallel cases (high current higher V drop across Rinternal).

Another point about those labs. No one bothered to fill out the ehadings on the first sheet of the lab report. While I admire your attempt to conserve the precious resource, ink, you will have to fill these out on each first page to receive full credit on this lab and all future ones. This goes for Honors as well. Name , Date of Lab performance, Period of your class, Lab group members who participated, must appear on the first sheet of all labs.

If R2 and R3 are in parallel with each other and then the pair is in series with R1, if R3 is disconnected, less current will flow through R1 so V1 across R1 must have decreased and V2 across R2 will increase because V1 + V2 still must equal Vtotal from the battery as before. Thus when R3 is disconnected, R2 will have more current through it, more voltage across it and produce more power. The reverse will be true for R1 when R3 is disconnected.

Electrons and currents

Currents are caused by moving charges and the measure of current is the number of coulombs passing by a point per second. IF a current is caused be electrons and each electron has a charge -1.6x10-19 Coulombs, then the number of electrons passing the point where the current, I, is measured is given by:

[I/1.6x10-19] electrons per second

We drop the - sign because we are interested in magnitude not direction. The - sign just means that the current is in the direction opposite the direction the electrons are going.