Physics 1c Practical -- SPRING 2008

Course Description

9 units (4-0-5)

Second term of an introduction to electricity and magnitism with an emphasis on learning from practical examples and applications. The assignments include activities using a take-home lab kit.

Spring 2008
Lecturer: David Politzer
e-mail: politzer@theory.caltech.edu

Post-Ditch Day recheduling:

Do not turn in your lab book for the first half of Experiment 12. (That had been due Wednesday, 5/21.) The whole of Exp. 12 is due Wednesday, 5/28, and it will be graded as a whole. We will staff the Help Lab on Monday, 5/26, as well as Tuesday, 5/27.

Homework problems originally due Thursday, 5/22, will not be considered late if turned in Wednesday, 5/28. The schedule for 5/29 and thereafter is unchanged.

Help Lab moves to Mondays

Help Lab will be staffed Mondays from 8:00 to 10:00pm -- and no longer on Sunday evening. Tuesdays (8:00 to 11:00) remain unchanged.

Physics or logistical questions may be directed to the lecturer via e-mail if you can't do it in person, e.g., before or after lecture, Tuesday help lab, his office, etc. Questions and answers that might be of interest to other students will be posted here: Q&A (without identifying the questioner by name). (There's one there right now.)

QUIZ SCORES: As per student requests, the class averages on the quizzes are: Quiz 1 = 8.4 +/-1.3; Quiz 2 = 8.9 +/-1.2; Quiz 3 = 9.0 +/- 1.2; Quiz 4 = 9.0 +/- 1.5; Quiz 5 = 6.7 +/- 1.9; Quiz 6 = 8.4 +/- 1.0; Quiz 7 = 8.7 +/- 1.4

As per request of ASCIT and the BOC, here is a copy of their policies form, filled out for Ph 1 Prac. (You'll want page 2, too.)

SOLUTIONS TO LAST TERM'S FINAL EXAM:

(These are gifs. The size that first comes up will depend on your browser configuration, and you might have to re-size them yourself to view comfortably.)

PROBLEM I

PROBLEM II

PROBLEM III

PROBLEM IV page 1 and page 2

NOTE:

Some of the .html documents contain footnotes that can only be accessed by clicking on little checked boxes.

LAB 9 ADDENDUM:

Here is an annotated version of section 4 of Experiment 9 (postscript, pdf, or html).

LAB 9 DATA:

In Lab 9, you'll need to know the masses of the nuts that are used to counterbalance the magnetic force between the coils. As last measured the nut masses were:

1/4"-20: 3.12 +/- 0.05 g

#10-24: 1.36 +/- 0.04 g

The "32" and "24" in #10-32 and #10-24 refer to the number of threads per inch, which is irrelevant to the way we use them. The current nuts are actually #10-24's (and not #10-32's).

MORE ON EXP 9:

One of our very dilligent lab book graders a couple of years ago provided further comments on the error analysis task of the first week of experiment 9. I've linked them here but can't resist adding that the labs require you to define and address tasks that are only generally suggested in ZAP!. There is almost never a single, right way to proceed. Regarding the discussion in the accompanying note, the as yet unmeasured shift in the small nut that would be required to counterbalance the magnetic force torque can be estimated (i.e., using the theory) in advance, certainly to an accurracy that would allow proceeding with the fractional error analysis that this note says you can't do. Rather than be discouraged by what appears to be professorial disarray, you should be encouraged to figure things out for yourself and do something that makes sense to you.

Here is the aforementioned note: in postscript and in pdf.

AND YET MORE ON EXP 9:

I don't know of any topic that so quickly touches upon epistemological, ontological, and teleological issues (maybe those should be vocabulary questions on the Ph 1c Prac final; certainly you shouldn't graduate without knowing them!) as the discussion of errors in science. It is easy to list (and not too hard to "derive" formulae purportedly relevant to large data sets. But what it all really "means" is another issue.

Here is yet another TA's attempt at explaining all this. Is it clearer? Do you need another? Is more material to read just more confusing? That's all a matter of taste and personality. Furthermore, the posting of these discussions is no guarantee of their value or correctness.

Click for postscript or pdf.

LAB 10 ALERT:

Your parts kit contained a sheet showing how to include from the start an additional capacitor in the circuit, as suggested and explained by Professor Pine (reproduced here, here, or here, depending on your software taste) . (The very latest printing of ZAP! has it in the text.)

Also, some of the op-amp pin-numbering diagrams from several years ago (including those on some of the previous years' Errata Sheets) are incorrect. The diagram on page 88 of ZAP! under "Detailed Schematic" is reproduced from a manufacturer's spec sheet and shows the convention generally used. Note that the figure shows the pins as viewed from the TOP of the integrated circuit. (The last few printings of ZAP! are correct.)

LAB 11 ALERT:

In Lab 11, you will build a x50 step-up transformer. The secondary is a 500 turn inductor, included in your kit. You wind a 10 turn primary. Sometimes a power supply built according to the instructions doesn't work because of arcing at the high voltage end of the transformer. To be on the safe side, you should consider the possible design improvements suggested here from the outset.

LAB 11:

The capacitor markings are somewhat obscure. For example:

label: 1 05 M ; 470 M ; 100 M ; 56 M ; .001 M or 102 M

value: 1 microF; 470 pF; 100 pF; 56 pF; 1 nF

General course info. (1/7/08) - the same as last term: see last term's Ph 1b Prac Info memo (postscript, pdf, or html).
Course Syllabus and Assignments (3/2/07) - postscript, pdf, or html .
Instructors (3/31/08) - instructors.
Ombudspersons (1/18/08) - Ombuds.

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