April 2014

        http://vip.vast.org

Hi everyone,

Hope you have survived the 3rd  9-weeks and a pretty wild winter.  Spring is finally here and we are looking forward to our annual VIP spring meeting at UVA later this month. It is coming fast! Hope to see everyone on April 26.  

In this issue we have:

• VIP Professional Development: More Modeling Instruction from the VDOE at the 2014 JMU CTA.
• 5 Quick Links: What’s happening in Physics and Physics Education
• From the Lab: Magnetic Field Around a Vertical Wire
• Big Ideas: The Big Ideas and Scientific Practices Behind AP Physics 1 and 2
• VAST mini grant
• The PLC: Professional development and professional organizations

I always look forward to taking the time to connect with great teachers from across the state.  I hope you make up to spend the day with us at the VIP Spring meeting.

Until then,

Timothy Couillard

President, Virginia Instructors of Physics (VIP)

Who: Physical Science, Physics teachers, and University physicists.    

When: April 26th (time agenda below) 8:30 AM – 3:00 PM

Where: Department of Physics Jesse Beams Laboratory, University of Virginia
382 McCormick Rd
Charlottesville, VA 22903

 There is a good web map at http://www.virginia.edu/webmap/GMcCormickRoadArea.html  The physics building is #41. You may want to park behind #38 off of stadium road. Do not park at the physics building. This is 24/7 permit parking.

Cost: Free!!! 

RSVP IF ATTENDING

 timothy_couillard@ccpsnet.net

Modeling Instruction at the 2014 James Madison University CTA

Thanks to support from the Virginia Department of Education, James Madison University, and school divisions statewide, Modeling Instruction Training for Physics, Chemistry, Biology, and Physical Science will return to the JMU Content Teaching Academy in 2014.  This year both Introductory and Advanced academies will be offered.

The program was recently featured in state and local media: http://goo.gl/OOyBlf

Contact Joe Mahler for additional information at joe.m.mahler@gmail.com.

1. Dot Physics: What is the Mass of Captain America’s Shield? http://www.wired.com/2014/03/whats-mass-captain-americas-shield/

2. Noschese:  Dynamics Problem Solving Template http://noschese180.wordpress.com/2014/03/03/day-101-dynamics-problem-solving-template/

3. NPR: A Physicist Gets 'Smoking Gun' Proof Of His Theory http://www.npr.org/blogs/thetwo-way/2014/03/18/291134088/watch-physicist-gets-smoking-gun-proof-of-his-theory

4. Watch the Trailer for Particle Fever: http://trailers.apple.com/trailers/independent/particlefever/

4. TED 2014: Allan Adams on the Discovery that Could Rewrite Physicshttps://www.ted.com/talks/allan_adams_the_discovery_that_could_rewrite_physics

©Modeling Workshop Project 2009        

For more Modeling Instruction curriculum materials, visit http://modelinginstruction.org/ to find a Modeling Instruction Workshop near you.

Purpose

Upon completion of this activity students should:

• Recognize that moving charge is necessary for a magnetic field to be present.
• Represent the magnetic field around a conductor or moving charge using the right curl rule.
• Distinguish between magnetic fields and the electric fields in terms of their origin (moving and static charge respectively) as well as their patterns (loops and lines, respectively).
• Recognize that like the electric field, the amount of influence decreases with distance from the field’s source.

Apparatus

Power supply

Resistor or rheostat

Wire

Compass

Ringstand

Cardstock

Pre-lab discussion

Pre-lab discussion should begin with a demonstration that a small compass will show a deflection when current runs through the wire. Using “top” and “bottom” sticky tapes and a simple circuit it can be shown that the compass is responding to a new field, distinct from the electric field.  This conclusion arises from the observation that:
1) the compass only responds when the circuit is closed and 2) both top and bottom tapes are attracted to the wire, indicating that it’s electrically neutral.  

The compass can be introduced as a “test” for the presence of a magnetic field.  The direction of the force on the north end of the compass is (arbitrarily) chosen to represent the direction of the magnetic field.  Charge students with the task of exploring this new field in the vicinity of a current-carrying wire.  What does it look like?  What happens when the direction of the current is reversed?   Qualitatively, what happens to the strength of the field as you move away from the wire?

Performance notes

        The setup for the lab is a circuit that contains a length of wire that passes vertically through a piece of cardstock.  The lab data sheet suggests positions to place the compass to determine the “look” of the field around the wire, when current is flowing in each direction.   The magnetic field produced by the current will cause the needle to deflect from North.  The direction of the force is the direction of the North end of the compass’ deviation from North.

Careful observation will show that the deflection of the needle is somewhat greater in the NW and SW positions than in the NE and SE positions when the current is directed upwards.  Students should also note that the compass deflection increases as the current increases.  In the post-lab discussion, help students to recognize that the final needle position is due to the superposition of the Earth’s magnetic field and field produced by the current.

Have students represent their findings on whiteboards.  Consider a roundtable discussion to elicit the main points of the lab; moving charge creates the magnetic field, the field lines form closed loops, and the field weakens as you move away from the source.  Because the direction of the field at a given point in space is defined as the direction of the force on the North end of the compass, the right hand “curl rule” should fall out as a natural consequence:  when the thumb of your right hand points in the direction of positive charge flow, the fingers of that hand naturally curl in the direction of the field.

Thus the picture of the field that is eventually settled upon should look like this (in the case of charge flow toward the viewer):

Introduce the convention of dots  to represent a field or current directed toward the viewer, and crosses  for quantities directed away from the viewer.

Measuring the magnetic field due to current in a wire

Purpose-Part 1

        The purpose of this experiment is to determine the relationship of the strength of the magnetic field around a current carrying wire and the distance of the field from the center of the wire.  The current is held constant.

• multimeter
• book
• switch
• paper
• rheostat
• power supply
• wire
• compass
• N-S line of the earth’s magnetic field

Apparatus

        Power supply, a compass with degrees marked around the circumference (preferably marked under the tip of the needle), a ruler, sheet of paper, wire, multimeter or ammeter (5 or 10 amp), rheostat (depending on power supply), switch, clamps, aluminum rods, tape, book

Procedure

Note: it is very important that this lab be done on a surface that has no current running underneath it, and no ferrous metal (chairs, steel legs, bolts, etc.) near or in it.  On some lab tables it is necessary to add an extension to the table and place the compass and paper on it to get away from ferrous materials.

1. Set up the equipment as shown above.  If the power supply used in the lab has a variable control, the rheostat is not necessary.  If a digital multimeter is used make sure the lead wire is inserted in the high amp hole.  Do not turn on the power supply yet.
2. Draw a line length wise through the axis of your paper.  Tape the paper to the table so that one end of the line is touching the wire and the line is oriented north and south.  To test this, move the center of the compass along the line.  The needle should always remain directly above the line.  If the needle lines up in some locations on the line and is deflected at other locations on the line, there are ferrous or magnetic materials too close to where you are working.
3. Measuring from the center of the wire, place a mark on your line 5 cm to 6 cm from the wire.  Then mark off five more points at increments of your choosing.  Data up to 30 cm have proven to be reliable.  Place the center of the compass on the line over the first mark.  In performing many trials, it was found that placing the compass closer than 5 cm to the wire produced poor data.
4. Turn on the power supply, close the switch and adjust the current to a value from 3.0 to 10.0 amperes.  Record the distance from the center of the wire to the center of the compass, and the angle the compass is deflected from north-south line.  Open the switch.  To avoid overheating the wire and other equipment, only close the switch when collecting data.
5. Move the compass to the next mark, close the switch, record distance and angle.  Repeat this process until at least five data points are obtained

Background and Magnetic Field Theory

N-S line of the earth’s magnetic field

d

Wire

Field lines



Table

The magnetic field due to a wire encircles the wire as shown in the diagram to the right.  The equipment is set up with the compass placed along the north-south line of the earth’s magnetic field.  Since the magnetic field around the wire is circular, if the compass is placed along the N-S line, then the earth’s field and that of the wire will be perpendicular to each other. The result will be a deflection of the compass needle somewhere between the N-S line of the earth’s magnetic field and the E-W line of the current carrying wire’s magnetic field, along the resultant of the two magnetic fields.

The deflection of the compass needle obviously depends on the relative strength of the magnetic field of the current carrying wire’s compared to that of the earth at the same location.  In the diagram above right,  represents the magnetic field vector from the wire and  represents the magnetic field vector of the earth. Since the strength of the Earth’s magnetic field remains constant during the experiment, we can say that .  A plot of tan  vs r will allow students to determine the relationship between the strength of the field and the distance from the wire.

Evaluation of data

Below is a sample data table for the lab and the modified graph produced from the data..

Since the actual value of the magnetic field strength was not determined, but is proportional to tan , students should be able to conclude that the strength of a magnetic field produced by charges moving in a wire is inversely proportional to the distance from the wire.

Purpose- Part 2

The purpose of this experiment is to determine the relationship of the strength of the magnetic field around a current carrying wire and the amount of current through the wire.  The distance from the wire is held constant.

Procedure

This experiment uses the same apparatus and techniques as part 1.  The difference is that the distance from the wire is kept constant at a value from 5 and 10 cm and the current in the wire is varied from 0 to 5 amperes.(More current works well but your power supply must be able to provide it.)

Students will use their data to determine the relationship between the magnetic field around the wire and the current in the wire.

Evaluation of data

Below is a sample data table for the lab and the graph produced from the data collected when the compass was placed 5.0 cm from the wire.  

Using the argument cited in part 1, students should be able to conclude that the magnetic field strength is proportional to the current in the wire.  With some encouragement, they should also be able to combine the proportionalities to state that  for the magnetic field produced by current in a straight wire. For quantitative problems, the constant of proportionality is , so the relationship is        

http://advancesinap.collegeboard.org/math-and-science/physics

The curriculum redesign for AP Physics 1 and 2 focuses around 7 big ideas and 7 scientific practices. What can you do with this?

The Big Ideas

Big Idea 1:Objects and systems have properties such as mass and charge.  Systems may have internal structure.

Big Idea 2:Fields existing in space can be used to explain interactions.

Big Idea 3: The interactions of an object with other objects can be described by forces.

Big Idea 4:Interactions between systems can result in changes in those systems.

Big Idea 5:Changes that occur as a result of interactions are constrained by conservation laws.

Big Idea 6:Waves can transfer energy and momentum from one location to another without the permanent transfer of mass and serve as a mathematical model for the description of other phenomena.

Big Idea 7:The mathematics of probability can be used to describe the behavior of complex systems and interpret the behavior of quantum mechanical systems.

Science Practices

SP1:The student can use representations and models to communicate scientific phenomena and solve scientific problems.

SP2:The student can use mathematics appropriately. 

SP3:The student can engage in scientific questioning to extend thinking or to guide investigations.

SP4:The student can plan and implement data collection strategies in relation to a particular scientific question.

SP 5: The student can perform data analysis and evaluation of evidence.

SP6:The student can work with scientific explanations and theories.

SP7:The student is able to connect and relate knowledge across various scales, concepts, and representations in and across domains. 

Opportunities for Physics Teachers

Need funding for an innovative curriculum activity?  VAST's minigrant application for funding is due June 1.  The application is short and can be found here:

http://www.vast.org/grants.html 

AAPT Summer Meeting: Minneapolis, MN July 26-30 2014 http://www.aapt.org/Conferences/sm2014/

James Madison Content Teaching Academy, June 23-27

http://cta.jmu.edu/

Matter and Interactions Distance Education Course

http://www.matterandinteractions.org/Content/HSteachers/teachers.html

Modeling Instruction Summer Workshops

http://modelinginstruction.org/information-on-summer-2014-workshops/

NSTA 2014 Area Conference: Richmond Virginia October 16-18

http://www.nsta.org/conferences/

"Science of Nuclear Energy & Radiation" 2014  4-DAY Science Teacher Workshop, http://local.ans.org/virginia/public_education.html

UVA Professional Development Opportunities in Physics Education http://k12.phys.virginia.edu/home.html

Virginia Association of Science Teachers Profession Development Institute (VAST-PDI) November 19-22, 2014 at the Hotel Roanoke.                                        http://www.vast.org/annual-pdi.html 

Woodbury School’s 2014 Open Lab Summer Institute, July 27-29

http://jacobsphysics.blogspot.com/2014/02/open-lab-2014-july-27-29-at-woodberry.html

VIP website:

Visit the Virginia Instructors of Physics website at http://vip.vast.org/

Are you on the email list?

If you have any physics-related questions, news, or anything else?  Please post it to the yahoogroup (http://groups.yahoo.com/group/va-inst-phys/) or send it to us directly.

Contact Info

President: Timothy Couillard (@coolyrd), timothy_couillard@ccpsnet.net

Vice-President: Jeff Steele,  jeffsteele1@gmail.com 

Webmaster: Tony Wayne, twayne@k12albemarle.org

Support

This newsletter and our spring meeting are graciously hosted by the Physics Department of the University of Virginia.  The Make&Take session is funded by the Virginia Association of Science Teachers (VAST) of whom we are an affiliate and Jefferson National Laboratory.  Spring meeting door prizes generously donated by Vernier, CPO, Sargent-Welch, Frey, Arbor Scientific.  

Thank you for all you do to promote physics education in Virginia and beyond!