## Section

This is our official class website, just like last year. Please look at it weekly to see assignments, advice, reminders, clues, cartoons, and notices.

You should always check here before you start your HW assignment, and you can subscribe so you'll get an email when I update it.
Physics can explain so much, such as what would happen if I pitched a baseball at 90% the speed of light (see here for the answer
• #### Open allClose all

• Instructions: Clicking on the section name will show / hide the section.

• You are using a computer and the internet right now and so you are using over 100 phenomena from the physics of electricity and magnetism. We will learn about dozens of those phenomena this year. It is an amazing story.

HW Tue: summarize the Demo of Charge you did on monday, including a sketch.  Show clearly where the electrons moved.

HW Wed:  hand in lab notes from electron transfer activity in class on Tuesday.  Include a short description of the set up.  You should report how many electrons are lost per second.  It will be a big number.

HW Friday: Study and learn the opening section before History in Wikipedia for Electricity (it starts "Electricity is the set of physical phenomena associated with the presence of electric charge").  I will give a reading quiz in class.

For next Tuesday: 16: Q-1, 2, 3, 4,6; summary of scotch tape static; getting to know the static charge physlets, see below.   (your HW for Tuesday is to open the site and make sure you can run the physlets and show me a printout (not hand-drawn) of each of them.)

http://phet.colorado.edu/en/simulations/category/physics is the site where you can find most of the physlets we'll use in class. You can select "electricity, magnets, and circuits" to get a shorter list. We'll look at "electric field of Dreams" and "electric hockey" first. Play with this for about 5 minutes.

Points:

• know what is difference between doing science and studying science
• Differentiate science and authority-based systems
• Be able to define/organize the scope of Phys II vs Phys I
• Be able to generate positive and negative static charge
• Be able to draw the topics map and fit in electricity
• Define and characterize charge

• For Monday: LABOR DAY HOLIDAY

For Tuesday: 16: Q-1, 2, 3, 4,6; summary of scotch tape static as assigned in class; Getting to know the static charge physlets, see below.   (your HW for Tuesday is to open the site and make sure you can run the physlets and show me a printout (not hand-drawn) of each of them.)

http://phet.colorado.edu/en/simulations/category/physics is the site where you can find most of the physlets we'll use in class. You can select "electricity, magnets, and circuits" to get a shorter list. We'll look at "electric field of Dreams" and "electric hockey" first. Play with this for about 5 minutes.

http://www.compadre.org/Physlets/electromagnetism/  this is another useful page, look at the "electric field" list and open "Field-Line Representation of Vector Fields".  This one will require you use IE or Firefox.  Move the charges around.    Toggle between vectors and lines.  In Config B, can you tell which charges are + and -  ?

(IMPORTANT NOTE: MANY TIMES, IF AN APP OR PHYSLET DOESN'T RUN ON A COMPUTER, IT IS PROBABLY THE FAULT OF THE WEB BROWSER YOU ARE USING.  SO IF CHROME DOESN'T WORK, TRY INTERNET EXPLORER.  IT IS YOUR RESPONSIBILITY TO FIGURE OUT HOW TO WORK THESE PROGRAMS.)

HW due Wed: 16: Q-7,8 P-1,2,3, 5, 7, 9     Another good link for static charges that you can run on IE or Firefox:    http://vnatsci.ltu.edu/s_schneider/physlets/main/efield.shtml.  try the various charge configurations, and press play to see the little charge move.

HW Friday: 16: Q-9, 10, 11; P-13, 15

HW due next Monday: read 16.7, 16.8; do 16: Q-13,14,15; P-23,25,27,29,33

quiz next Tuesday : on Coulomb's Law and forces

Points:

• Describe when induction will occur and its effects (on conductors and insulators)
• Describe conduction and induction cases for electroscope practicum
• Be able to do simple coulomb’s law calculations
• Be able to apply vector math to do 2-D coulomb’s law problems
• Know that Coulomb’s law is complete for electrostatics, not complete for electrodynamics
• HW due Monday: read 16.7, 16.8; do 16: Q-13,14,15; P-23,25,27,29,33

quiz Tuesday : on Coulomb's Law and forces, and for this quiz, memorize the value of k

HW due Wed: 16: p-17a, 31, 57, 32, 41, 55; and Faraday cage lab memo report

HW Due Thursday: using http://vnatsci.ltu.edu/s_schneider/physlets/main/equipotentials.shtml (in IE or Firefox) this link, find all positions in all 7 of the Charge Configurations where the E field is zero.  Be prepared to show the class.  If you place the green test charge at this location, it should not move.

We will conduct the pith ball minilab on thursday in class.

HW due Friday:  16: p-11, 26, 62 (use kinematics and F)   Write the hypothesis for the lab, and show me the relation for qtotal as a function of d, m, g, k, and q and calculate a value for q on each pith ball.
Note, data for the lab in J: drive and I will keep posting new notes on Measuring Coulomb's Law in FILES.

HW due next Monday:
17: Q-1-5; P-1,3,5,7,11;   Show me a draft of the report.  This should be typed and all the parts finished.   use this physlet to prove that Work=0 if you move along an equipotential line for any of the Charge Configurations; bring printed page --  http://vnatsci.ltu.edu/s_schneider/physlets/main/equipotentials.shtml  .

HW due next Thursday:   The complete formal report of Measuring Coulomb's Law is due.

Points:

1. Be able to describe lightning with physics of charge, induction, and ionization
2. Sketch field lines for 5 basic cases of charge
3. Relate electric potential to gravity potential
4. Relate V to E
5. Relate equipotential lines to contour (topo) map

• HW due Monday:
17: Q-1-5; P-1,3,5,7,11;      use this physlet to prove that Work=0 if you move along an equipotential line for any of the Charge Configurations; bring printed page --  http://vnatsci.ltu.edu/s_schneider/physlets/main/equipotentials.shtml  .

HW due Tuesday:  Coulomb pith ball numerical calculation due, using the data you obtained in the lab, will be handed in.  Make your calculation clear and readable.
Draw E-field lines and equipotential lines for each of these:  1).  2 equal positive point charges  2).  2 positive point charges of 1 and 3 q each  3)  a triangle with a negative point charge at each vertex.   4)  a very long line of charge

HW due Wednesday: Show me a draft of the Coulomb lab report.  This should be typed and all the parts outlined..
An equilateral triangle with sides of 2.0m has a point charge of +1mC at each apex.  a) carefully draw the E field lines and isopotential lines.  b) what is E at the center of the triangle?  c) what is V at the center?

Thursday. RETREAT

HW due Friday  RETREAT

HW due next Monday: Gauss's Law: 16: 39, 41,43,47.  Also, show that Coulomb's Law E=kQ/r2 can be derived from Gauss's Law.  (Recall that k = 1/(4πεo)

HW due next Tuesday, 26 Sep:   The complete formal report of Measuring Coulomb's Law is due.

Points:

• Understand Gauss's law, and use it to derive Coulomb's Law for a point charge
• Be able to describe lightning with physics of charge, induction, and ionization
• Sketch field lines for 5 basic cases of charge
• Relate electric potential to gravity potential
• Relate V to E
• Relate equipotential lines to contour (topo) map
• NOTE: for the exam in one week, you need to recall that F=GMm/r2 and how it is applied.  You don't need to memorize the value of G.

HW due Monday: Gauss's Law: 16: 39, 41,43, 47.  Also, show that Coulomb's Law E=kQ/r2 can be derived from Gauss's Law. -- Recall that k = 1/(4πeo)  YES, we did this in class, so if your notes are neat and legible, show me that.  If not, then write it neatly for me to review.

HW due Tuesday, 26 Sep: The complete formal report of Measuring Coulomb's Law is due

HW due Wednesday: you are off somewhere learning about college.   The study guide is posted.

Thursday: 16: Q-22 and P-67. chapter 17: MCQ-1,2,3,4,5,6; p-8, 13  and you didn't show me this, so be prepared.   use this physlet to prove that Work=0 if you move along an equipotential line for any of the Charge Configurations; bring printed page --  http://vnatsci.ltu.edu/s_schneider/physlets/main/equipotentials.shtml

quiz: given a charge, you will calculate properties of field or potential.

HW due Friday:  Do chapter 16 MCQ 1-13 (all of them); write each of chapter 16 classic problems on a page and make a diagram for each.   Slides for both 16 and 17 will be posted.

HW due next Monday: Exam 1 in class.  It covers up through section 5 in chapter 17.

For fun only, use the Davidson physlet to test if you can put the test charge into orbit around a single or multiple negative charges, or can you make the test charge hover in one place?.  (double click to create new equipotential lines) bring in a printout

If you're really good, you can show that the particle bounces between the same value potential lines.

points.

• Be able to describe lightning with physics of charge, induction, and ionization
• Name and sketch the 10 main problems for the exam.
• Sketch what happens to an insulator in an E field
• Show how to quantify V from a point charge in space
• some thoughts about repulsive charges:   http://what-if.xkcd.com/140/

Monday: exam 1.   bring two colors of pencil.

HW due Tuesday:  17: Q:6,7,8,9; P-2,4,6,10

HW due Wednesday: 17:P-15, 17, 19, 21, 23, 25 use this physlet to put the test charge into orbit around a single or multiple negative charges, or can you make the test charge hover in one place?.  (double click to create new equipotential lines) bring in a printout  http://vnatsci.ltu.edu/s_schneider/physlets/main/equipotentials.shtml

HW due Friday:  17: Q-10,18; P-35, 37

HW due next Monday:.17: P-39, 43, 49, 53, 57

NEXT TUESDAY: 17:q-11, 12; P-68,69,71,73,74,77 (be sure to consider all positions on the line)  Also, calculate the design for a capacitor to hold 1.0nC using only a AA battery and one two layers of metal separated by a sheet of plastic wrate, report area and separation.

Next week: capacitor lab introduced.

goals for this week:

1. describe how a capacitor works
2. design a capacitor of a given C by adjusting d and A
3. be able to describe the role and effect of dielectric materials in a capacitor
4. be able to describe 6 fundamentals of lightning
5. describe the energy stored in an electric field and quantify it.
• HW due Monday:17: P-39, 43, 49, 53, 57
We will discuss the lab to be conducted on Thursday and Friday

Due TUESDAY: 17:q-11, 12; P-68,69,71,73,74,77 (be sure to consider all positions on the line)  Also, calculate the design for a capacitor to hold 1.0nC using only a AA battery and two layers of aluminum foil separated by a sheet of food plastic wrap: report area and separation

HW due Thursday: Two groups will perform lab in class .  Your prelab is due as soon as you walk in the lab.

• This HW you will work on when not doing the lab these two days.
• 17: P-45, Search&Learn (S&L) p 500: #3 on lightning; and read 18 sections 1-3,
• show problem 77 a and b using the physlet below, sketch on printout the elevation of the potential as we did in class, bring printout to class;    then do the same for two equal negative charges, bring printout.
• http://vnatsci.ltu.edu/s_schneider/physlets/main/equipotentials.shtml

HW due Friday: Your first reading assignment is due for hand in.  You should read and report on chapter 2 of WHNI.  See the handout if you are confused.
Two more groups will work on the lab, and others will review HW and lab analysis.  bring your computers if you want to work on your lab.

HW due next Monday: 18: Q-1,2,3,4,5; MCQ-1,3,4,5; P-1,3,5  Look at this physlet: http://phet.colorado.edu/en/simulation/capacitor-lab

• HW due Monday: 18: Q-1,2,3,4,5; MCQ-1,3,4,5; P-1,3,5  Look at this physlet: http://phet.colorado.edu/en/simulation/capacitor-lab

HW due Tuesday:  17: P-85, 88, 93 (hint: find the travel time between plates first); also have your data for the lab plotted (each person should have the data and the plots)

Wed:  Bring a plot of your data as described for parts 1 and 2.  NOTE;  I have attached in files an example of the analysis section for the lab.  You are allowed to cut and paste from this section, and you are free to borrow equations and ideas from it.  I do expect you to understand it and derive your own numbers based on your data.

Also due Wednedsay: Do these 3 problems below.

x1: A capacitor of 25mF is charged to 444V.   It is connected to an identical capacitor.  What is the new voltage on each?  They are then disconnected.  What is the final voltage on each.

x2: A Leyden Jar of capacitance C is connect to a battery with potential V.  It is disconnected from the battery, and then connected to another jar of capacitance 3C.  a. What charge is on each jar?  b. What potential is on each jar?

x3: A variable capacitor is charged with a given potential.  a. What is this initial charge?  the capacitance is then quadrupled.  b. What is the new charge?  c. what is the new potential?

Thursday and Friday:   CONFERENCES

HW due next Monday: Capacitor Lab is due.

Goals for this week

• Show that electrical current, I, is an outgrowth of charge and time.
• Understand the parallel of electrical flow and water flow
•   Be able to describe that V is the potential for work, and I (current) represents real energy expenditure
•    Show ability to use I = V/R
• Welcome back.  If any of you wish to know what I reported to your parents/guardians during the conferences, please see me and I'll happily tell you.  If they didn't come to conferences, but you want to know, I'll happily tell you.

http://www.jpl.nasa.gov/news/news.php?feature=4340 is about a moon of saturn that holds a static charge.  How does it get charged?

Note: the next Reading Assignment using Chapter 5 of "We Have No Idea" is due Monday, 30 Oct. Start reading.

HW due Monday: Capacitor Lab is due.

Due Wednesday:  18: Q-6, P-7, 9, 11, 13; Look at physlet for Ohms Law: bring printout of lowest or highest current possible on it.http://phet.colorado.edu/en/simulation/ohms-law

Due Friday:  18: Q-7,8, 9,10,11; P-23, 27, 29, 31,33    Bring your VOM to class.  This is now part of required materials.

HW due next Monday: 18: Q-14,15,17,16; P-34,35,37,38,64,69;

Goals for this week

•   Understand the parallel of electrical flow and water flow
•   Be able to describe that V is the potential for work, and I represents real energy expenditure
•    Show ability to use I = V/R, P=IR
• Be able to set up a power-loss problem in transmission lines.
• HW due Monday: 18: Q-14,15,17,16; P-34,35,37,38,64,69

Due Tuesday: calculate R (for two lengths), P at burnout, and ρ for nichrome wire from demo on Monday

HW due Wednesday; 18: P-55, 77, 80

Due Thursday: If you didn't get 3 points for the Calculations and Analysis section of your Capacitor Lab, your corrections are due Today.

word of the day: Physic

HW due Friday: We will have a quiz on Ohms Law and Power in a lightbulb.

next Monday: Exam 2 in class

goals for this week

1. show how to solve power problems for simple devices in a circuit
2. show how to solve power problems for transmission from generator/source to user over a wire
3. derive a short list of classic problems for chapter 18
4. show that you can measure resistance, current, and voltage with your VOM

physic     [fiz-ik]

noun

1.a medicine that purges; cathartic; laxative.

Example:   Do not take a physic before physics class!

• http://what-if.xkcd.com/16/ is a little Q&A about lightning.  You are becoming experts on lightning, so here's some interesting info.

HW due Monday: Exam 2 in class.

Tuesday: 19: Q-7,  P-1, 4,5, 7, 9, 13   In Class: Ohm's Law Minilab: You will measure V and I for some objects and we'll share this data for determining R

HW due Wednesday:  19:  Q-10,11   P-15, 31,19  Bring VOM for a practicum in class.

HW due Thursday:  bring Excel plots for V vs. I data for each object in the minilab

HW due Friday: 1. There is a solid copper cylinder with a net negative charge.   Draw an end view of the cylinder showing 8 E-field lines and 6 isopotential lines wherever they would exist.

2. A transmission line carries electricity from the power plant to the factory.  Explain in words why power losses in the transmission line are decreased when the transmission voltage is increased.

3. We have found there is a voltage drop and a power loss across a resistor in a circuit.  Where do those volts go?  Where does the power go?

4.  Draw the circuit you used in the Ohm's Law minilab.  If the red and black wires you used had significant resistance, would this give you an error in the measurement of R of the object being tested?  If so, would that make R higher or lower than it should be?

5.  A capacitor with a dielectric has C=33.3 mF and is charged to 444V.  The dielectric is removed by slowly pulling it away.  How much work was required to pull the dielectric?

HW due next Monday: do these practice problems.

6.  I have five 15W (nominal) light bulbs that normally operate at 12V.  I connect them in series.  How many total Watts do they produce?

7.  Two charges of -q and -3q are on a horizontal line a certain distance apart.   Show the E-field, the isopotential lines, and the V profile plot.  Also mark any positions where E or V could be zero.

8.  I shoot a proton at 106 m/s directly toward a charge of +2e that cannot move.  How close does the proton get to the charge before it stops?

9.   Assume we each have 1.0 MΩ of resistance from L-hand to R-hand, through our body.  If the class of 14 formed a ring, holding hands, what would be the measured resistance across one person's hands?  Across 2?  3?

10.  Looking at the xkcd above, how far can you be from our 15m flagpole and still be safe from a direct lightning strike?  (ignore the building and assume the ground is flat).

due next Tuesday: the Ohm's Law Minilab.  Turn in the excel table, and make sure it is complete and neat and pretty, with headings, units, and clear descriptions of each row.  Also, include a paragraph commenting on why you think there is a difference between the 3 values for the colored resistor.  Note, you cannot list operator error or some other lame excuse.  Delve into the measurement in some way.  Note, you must talk about the tolerance value for this resistor.

goals for this week:

• show how to solve simple circuit problems with resistors and power source
• apply kirchhoff rules to solving more complex circuits with multiple power sources
• HW due Monday: do these practice problems.

6.  I have five 15W (nominal) light bulbs that normally operate at 12V.  I connect them in series.  How many total Watts do they produce?

7.  Two charges of -q and -3q are on a horizontal line a certain distance apart.   Show the E-field, the isopotential lines, and the V profile plot.  Also mark any positions where E or V could be zero.

8.  I shoot a proton at 106 m/s directly toward a charge of +2e that cannot move.  How close does the proton get to the charge before it stops?

9.   Assume we each have 1.0 MΩ of resistance from L-hand to R-hand, through our body.  If the class of 14 formed a ring, holding hands, what would be the measured resistance across one person's hands?  Across 2?  3?

10.  Looking at the xkcd above, how far can you be from our 15m flagpole and still be safe from a direct lightning strike?  (ignore the building and assume the ground is flat).

due Tuesday: the Ohm's Law Minilab.  Turn in the excel table, and make sure it is complete and neat and pretty, with headings, units, and clear descriptions of each row.  Also, include a paragraph commenting on why you think there is a difference between the 3 values for the colored resistor.  Note, you cannot list operator error or some other lame excuse.  Delve into the measurement in some way.  Note, you must talk about the tolerance value for this resistor.

practice problems 19: P-81,82

Wednesday: FINALS START  Good luck.

is a handy and quick solution for solver in the TI-89; it gives the example below.

2x+3y+10z=28
3x+2y+4z=16
x+9y+2z=11

1.) [2nd] custom, or until the f1 on the toolbar is "var"
2.) f3
3.) 4
4.) solve( and , {x,y}) should appear
5.) type in the following
solve(2x+3y+10z=28 and 3x+2y+4x=16 and x+9y+2z=11, {x,y,z})
6.) enter

The answers are: x=2, y=0.5, z=2.25

• Wecome to Term 2, where we get to learn magnetism!

Note: the next Reading Assignment using Chapter 16 of "We Have No Idea" is due Monday, 4 Dec. Start reading

HW due Monday: none.  If you are not happy with your final exam score, please come see me

HW due Tuesday:  read section 19-6; do 19: Q-17, P-49, 50, MCQ 8, 9, 10, 11

Wednesday: none

HW Due Thursday:  19: P-72;  Look at Figure 19-48, replace the 990Ω resistor with a 2.0mF capacitor, and calculate the equivalent R of the remaining two resistors, and then plot V vs. t for the capacitor for up to 5τ;

HW due Friday:  19: P-69, 73 ; for a simple RC circuit of 1.0 V and 1.0 Ω and 1.0F, plot Vcapacitor for up to 5s;
And use your VOM to measure the current from the batteries in a battery-powered device, such as your calculator. Report the I, V, and power of the device.

do RC minilab in class.

[Open-note quiz on capacitors and RC circuits.]

HW due next Monday:  Reading Assignment using Chapter 16 of "We Have No Idea"
Part 1 of the RC lab is due: what is R and C for those data and show how you obtained it.  19: Q-15, 16; P-19, 70, 93, in problem 81,  replace the 85ohm resistor with a 25mF capacitor.  Write the complete V and I curves for the capacitor and both resistors.

Points for this week:

• Know the risks associated with electricity.
• Know the safety rules.
• Master the V and I graphs for RC circuits.
• HW due Monday:  Reading Assignment using Chapter 16 of "We Have No Idea"
19: Q-15, 16; P-19, 70, 93, in problem 81,  replace the 85ohm resistor with a 25mF capacitor.  Write the complete V and I curves for the capacitor and both resistors.

HW due Tuesday:   19: Q-18, 20; P-52, 55;  design and sketch a circuit with τ = 1.0 s ;
Part 1 of the RC lab is due: what is R and C for those data and show how you obtained it.

HW due Wednesday:  COLLEGE VISIT DAY FOR 11TH GRADE        today, Dec 6, is the 230th anniversary of which invention?

HW due Thursday: 19: P-51, 74, 95.  All four tables will do the RC lab.  You will have 20 minutes on the apparatus, so I'm counting on you to know the procedure.

HW due Friday:  show me the R and C calculations and results for your lab.   quiz on safety

HW due next Monday:  NOTE CHANGE OF DUE DATE!   (for15 points) The RC Lab report is due. RC lab (see assignment sheet), ,   Include your Loggerpro data with any line fits you use in the report.

Schedule:

Mon: review your RC minilab data and continue RC circuits
Tue:  safety/hazards
Wed: safety
Thurs: summary, problems, and practice for chapter 19
Friday: problems, quiz on hazards and safety

Points for this week:

• Know and be able to list the risks associated with electricity.
• Know and recite the safety rules for the lab
• Master the V and I graphs for RC circuits; be able to draw for 3 types of RC circuits
•
• HW due Monday:  (for15 points) The RC Lab report is due. RC lab (see assignment sheet): analyze the data you collect on the #1 and #2 capacitors and your group's resistor; calculate R and C as we did in class, and then measure R using your VOM and read the C of the capacitor, and turn in the report; which includes name, date, lab title, analysis section + circuit diagram.  Include your Loggerpro data with any line fits you use in the report.

Due Tuesday:  You will do a simple circuit practicum in class, which will be due Thursday.   I will build a simple circuit.  You will, as a group, measure V across each resistor, and all currents, using your VOM.  I will assign a person to measure one item, so you need to be ready to use your VOM in this task.  Then, for Thursday, you will show me a schematic of the circuit, each measured value, and using the measured R and V, calculate the I values.  Compare the calculated I to the measured I values.

this actually works.  Can you explain how?      .

Due Wednesday: 19: p-21, 22, 58,86, 89  I gave you a new RC circuit to solve; prepare plots of V and I; Count how many GFI outlets are in your home.  Test one by turning it off using the "TEST" button, and verify what part of the house was affected.

Due Thursday:  19: P-87,  Practicum circuit lab report.   I need a clean and large schematic diagram of the circuit, with labels on each element, and also show the table of R, V, Imeas, Ipredicted, %diff (of I) for each resistor.

Due Friday:  If you guys plan it, we can have a party.  is somebody bringing hotdogs?

Due next year, Tuesday,  2 January 2018: 20: Q-1,2,3; bring VOM to class.   And a reading report on chapter 8 "What Is Time?" of your book WeHaveNoIdea.

Friday: view video of manufacturing flash memory cards:

• Welcome back.   158 years since Maxwell published his major work on E&M.

Due Tuesday, 2 January 2018: 20: Q-1,2,3; bring VOM to class.   And a reading report on chapter 8 "What Is Time?" of your book WeHaveNoIdea.

HW due Wednesday: Plot V and I vs t for this circuit: a 1500V battery is powering a circuit of a 2500mF capacitor and a 5.00kΩ resistor.

HW due Thursday: 20: Q-4-8.  Battery resistance lab--you are going to design and conduct.  Given a battery, how will you determine its internal resistance experimentally, using only one or two VOMs and a resistor?  You will have 25 minutes to work on this  ; Find the internal resistance for each of 2 batteries.  Your results are due by the end of class.  Hand in your data, a circuit sketch, and a table showing battery type, V, I, R and r for each.

HW due Friday: Study this PHET http://phet.colorado.edu/en/simulation/magnets-and-electromagnets ; how many revolutions does the compass make as it is moved completely around the magnet; and be prepared to answer other questions using this app.

HW due next Monday   Read Chapter 20 sections 1-5.  Prob 20: P-1-5

we will Build a homopolar motor in class

goals for this week:

1. know what a magnet is, know how the earth is magnetic
2. show how a current can cause a magnetic field (a moving charge causes a field)
3. show how a charge moving in a field has a force on it. (a moving charge causes a field!)
4. revitalize your learning of mechanics so you can explain the physics of car crashes

This is The Magnetic Fields

• HW due Monday:   Chapter 20 sections 1-5;   Do Problems 20: P-1-5
*Perform deflection of an electron beam parallel and perpendular to the Earth's B field.  Record method and data in class.  Minilab writeup is due Wednesday.

HW due Tuesday: 20: Q-6-12; P-7, 8, 9,11,12, 13, 25

HW due Wednesday:  Minilab on CRT in a solenoid is due in class.  Predict and compare the distance of deflection in the CRT (you have data, and assume path length of electron inside the CRT tube is 11.cm), and show in a sketch that the deflection was in the correct direction.  Refer to your notes that you should have taken.

HW due Thursday:   read this article http://www.physics.org/article-questions.asp?id=51 and look up additional info to answer these questions: 1. how much sunlight power strikes the ground per squre meter (intensity)  2.  what is the photoelectric effect?   3.  how are the freely migrating electrons in the solar cell forced to move in one direction to form a current?   Solve this practice problem: I am standing with a compass held horizontally.  3.0 m West of me is a long horizontal wire pointing straight South.  What current in the wire will produce a field of 0.5G where I am?  If I do produce that field with that current, will it affect my compass?  Show the diagram!

I'll hand out the next lab on current carrying wire in a B field.  Does anyone want to demo the force on the wire antique.  Let's learn how to find the voltage of a USB charger

HW due Friday:    Mr. Reid Sebion of All Energy Solar will be our guest to talk about solar power technology.

HW due next Tuesday:  http://phet.colorado.edu/en/simulation/magnet-and-compass  be able to describe planet earth’s magnetic field, including declination. Check all the boxes at right in physlet for best demo. bring printout of physlet.  Why is field stronger at the poles?

HW due next Wednesday:
Write the equations and analysis needed to complete the lab on magnetic force and a wire, this should be 1/2 page of text and equations.

Schedule

Review in the lab the key themes so far in electricity and magnetics

Thursday: introduce Lab: Magnetic force on a wire

handout on Ampere’s Law and Magnetic Permeability

study guide for exam 1: 90 pts.  know RC circuits (charge and discharge), graphs of them, how and why capacitors behave as they do, electrical safety (again!), simple magnetism concepts (field lines, earth, attraction), and magnetic field from a straight wire (magnitude and direction)

• HW due Tuesday:  http://phet.colorado.edu/en/simulation/magnet-and-compass  be able to describe planet earth’s magnetic field, including declination. Check all the boxes at right in physlet for best demo. bring printout of physlet.  Why is field stronger at the poles?

HW due Wednesday: Write the equations and analysis needed to complete the lab on magnetic force and a wire, this should be 1/2 page of notes and equations; each person to present prelab. For prelab discussion: be prepared, bring notes and all lab materials. Your grade will be based on ability to answer questions about the lab. In 2 minutes, you will explain to me what you will do in the lab and for analysis.  If you haven’t prepared well, I will stop the discussion and you’ll have to find me later.

HW due Thursday:  Lab "Magnetic force on a wire" in class.  If you can't do your lab in this class, all members of the group must find time to do it together by Tuesday.  Groups will be assembled on Wednesday, depending on who is ready.

HW due Friday:   20: P-9,11,13,27, 29, 33

HW due next Monday: 20: P-69, 71, 60 and any that you've fallen behind on in Chapter 20.

next Tuesday:  exam 1, chapter 19 and up through section 20-5.

Points / learning goals for this week.

• 1. solve problems for a moving charge in a field or a current wire in a field
• 2. describe and quantify a field around a current wire
• 3. describe and quantify the forces between current carrying wires
• 4. understand the lab for wire in a field, and be able to conduct all portions
• HW due Monday: 20: P-69, 71, 60 and any that you've fallen behind on in Chapter 20.

HW due Tuesday: exam 1 in class.

HW due Thursday: show me your analysis of all your group's lab data; you should calculate B values for each run.  Each person should create their own table in Excel for all your calculations; if you have already done hand calculations, do them again in Excel to compare.  Each person should build their own table.

HW due Friday:  20: Q-13, 15, P-15, 17, 31

HW due next Monday: 20: Q-16,18 P-38, 49, 54

Schedule:

Fri: demos (wire and battery); 20-8, 20-9

Points:

1. show how magnetic forces affect a loop of current in a B field.

2. master the topics of magnetism with the HW

• Keep your eyes open for summer STEM camps at the universities.  They start coming out in February.

We have an exam on 15 Feb.

HW due Monday: 20: Q-16, 17,18 P-38, 49, 54

Tuesday: this is a work day for your lab teams.  Bring computers.

HW due Wednesday: 20: Q-19, 20,21,P-53, 64,73

HW due Thursday:  show me your slides for the presentation of the lab

HW due Friday: presentations on Lab (force and a wire.)  see handout, with the following additional question:  if L is off by 1mm, what error will propagate to B?

HW due next Monday: 20: P-55,81,84,91 Search and Learn-1,5

Points:

1. Show how to use Ampere’s law to find B in a torus
2. Demonstrate how torque on a current loop is derived
3. Be able to describe the motor and voltmeter applications of torque loops
4. demonstrate all the calculations necessary for the lab
• Time for another read in WeHaveNoIdea.  Chapter 11 is very interesting.  Please have a report, at least 1/2 page of typed content, ready by Feb 20.

HW due Monday: 20,P-55,81, 84,91 Search and Learn-1,5 ;

HW due Tuesday: 21: Q-1-4, P-1,3,5,9, 12; 3 practice problems in FILES  "physics II practice questions for chapter 20".

HW due Wednesday: 21 Q 5; P-6,7,11 MCQ 2, 3.  there will be a quiz on wednesday.

HW due Thursday: perform magnet drop minilab

HW due Friday: Do #1 in Hoover Dam assignment in FILES. (you will have to read ahead for the simple transformer calculation.)  Study this physlet: (it will be quizzed) http://phet.colorado.edu/simulations/sims.php?sim=Faradays_Electromagnetic_Lab; Look at Pickup coil, Generator and Transformer tabs:

HW due next Monday:   21 : Q-6, 7,8,13, 14;  P-13, 14, 15, 17, 19

Schedule:  Exam 2 is 15 Feb. It will cover chapter 20 and sections 1-2 of chapter 21.  The only study guide is the practice problems due Tuesday.

Demos: RFID chip for function, flashlight, toothbrush; in class project on induction

1. Give each group a device
2. .Give them 20 min to work out .....
1. Identify mag fields with NS directions
2. Explain how device works in terms of magnetic and currents, show equation
3. .Produce a sketch to turn in with names attached
3. Present: person who contributes least to discussion in group will present for 3 min

Points:

1.Calculate induction for simple systems using faraday’s law

• HW due Monday:  21 : Q-6, 7,8,13, 14;  P-13, 14, 15, 17, 19

HW due Tuesday: I invented a gun that can shoot around a corner.  It shoots electrically charged bullets that take advantage of the earth's field.  I want it to curve at 10.0g bullet with a radius of 5.0 m when shot at 1000m/s.  How much charge must I put on the bullet, and where on the earth can I shoot it to curve to the right around a corner.

HW due Wednesday: do "09 practice problems for exam 2" in FILES.  Also see the list of equations on this that will be on the exam.

Due Thursday:  exam 2 in class

HW due Friday:  no school!

HW due next Monday: no school

HW due next Tuesday: problems 4, 5, and 6 of the Hoover Dam problems   Hand in a report, at least 1/2 page of typed content, of Chapter 11 in WHNI book.

Due next Wednesday: minilab on magnet drop.  See slides for details.  This is the analysis section of a report.  Show clearly the following: 1.  Direction of current according to Lenz. 2. Find B for each curve and show derivation. 3.  Derive and find dB/dx for a given position of the magnet or a given position on the curve.  4. How to improve the lab.  Type text, and equations and sketch may be hand drawn neatly with ink.

Exam 2 is 15 Feb. It will cover chapter 20 and sections 1-2 of chapter 21.  The only study guide is the practice problems due Friday.

Lab on induction and transformers: next week

Schedule: we will cover all sections of chapter 21, but only part of 21-6 (I will do eddy brakes)

Demos: RFID chip for function

in class project on induction

1. Give each group either a galvanometer and coil or speaker
2. Give them 20 min to work out
1. Identify mag fields with NS directions
3. Explain how device works in terms of magnetic and currents.
4. Produce a sketch for hand in with names attached
5. Present: person who contributes least to discussion in group will present for 3 min

Physlets: PHET on induction

• Points: I gives B, does B give I?
• Know faraday’s law and Lenz’s law, be able to apply them to 5 main situations
• Describe 4 ways to change magnetic flux
• How does changing mag flux produce an electric field?
• This section

HW due Monday: no school

HW due Tuesday: (a few students gone on show choir trip) problems 4, 5, and 6 of the Hoover Dam problems.  The reading assignment from WHNI is due today, chapter 11.

Due Wednesday: minilab on magnet drop.  See slides for details.  This is the analysis section of a report.  Show clearly the following: 1.  Direction of current according to Lenz. 2. Find B for each curve and show derivation. 3.  Derive and find dB/dx for a given position of the magnet or a given position on the curve.  4. How to improve the lab.  Type text, and equations and sketch may be hand drawn neatly with ink.

HW due Thursday: I spin a vertical circular 0.30m2 coil at 100. rad/s in a horizontal magnetic field of 0.50T.  The coil has R of 0.33 Ω and has a mass of 0.40kg.  a)  How much EMF is produced?  b) how much current is produced?   c)  how much electrical power is produced?   d) how much mechanical power is required?  e)  how much torque is required on the loop?  f)  how much work is done in 1.0 minute?   g)  could you power your smartphone during talk mode?  (note, you need to remember aspects of rototational motion)

HW due Friday: do the assigned problems (39,40,41,49,50,52,53,54,55, 56) from CMC98elec posted in files

HW due next Monday: bring to class exam 2 from this term, also view this video and explain why the droplets don't travel further up the knittin' needle

Our goals this week:

• introduce transformers and understand how they work
• understand the main points for exam 2
• be able to describe and use Faraday's Law and Lenz's law for simple geometries.

Practice problems in class.

1.  A square loop of length L, resistance R, mass M, is vertical and is lowered into a uniform horizontal field B at speed v; assume the loop is entering the field for each answer.  a) what EMF is induced?  b) what current? c)  what force is induced in the loop?  d)  If the loop is dropped freely, what terminal speed will finally be achieved?  e) how much heat will be generated as the loop enters the field completely?

2.  Describe the path and kinematics of a proton shot at the following:  a)  an E field pointing down  b) a B field pointing down  c) a long wire with current pointing down d)  a RH solenoid with clockwise current pointing down  e)  a simple bar magnet with North pole down

• MONDAY: NO SCHOOL

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