Re: First EM lab

[Herbert H Gottlieb <herbgottlieb@JUNO.COM>]

 

On Sat, 12 Jan 2002 14:01:25 -0600 Tina Fanetti <FanettT@QUEST.WITCC.CC.IA.US>
> I am trying to figure out what lab or lab activities to do for the
> first lab in intro calc physics EM. We only have one Farady ice pail. >
> We do have the stuff to map electric field lines...the lab write-up
> I have includes both magnetic and electric field lines...although I
> could rewrite it. 
> The other option is to start with circuit stuff.
>
> Thoughts ???

 

I'm sure that there will be a great deal of professional disagreement with my philosophy .... but I'm willing to sit up and listen to those who care to rebut these suggestions, based on many years experience writing, teaching, and grading introductory physics labs on the high school, community college and senior college levels.

 

Since this is an introductory lab, I suggest that you present some very simple oral instructions that take no more than five minutes.  Furnish each student with an "identical" set of apparatus which includes: a steel bar magnet and a tiny magnetic compass. Also furnish each student with a sheet of xeroxed paper 

prepared with an outline of their bar magnet and several labelled starting points printed around the north pole position of the bar magnet.

 

Instruct the students on how to use the old, conventional, head-to-tail compass method to plot the magnetic field lines around the bar magnet.  But, no matter how careful a student is, the two halves of his or her magnetic field plot will probably not be symmetrical.  Furthermore it is unlikely that all nearby students will have identical patterns. 

 

A post-lab discussion of the lab class results can be very profitable. Instead of merely stating that all of the variations were due to "experimental error", the students should learn how to look for, and verify that, other possibilities exist, such as: stray magnetic fields in the lab caused by magnetized steel girders and iron pipes in the walls and the floors; poles of some bar magnets which are not all located at the magnet ends; and small magnetic compasses which point in the wrong direction because their polarity has been reversed.

 

In conclusion, I propose that the first EM lab is designed to use very simple  equipment, simple procedures, and great possibilities for error that the students can learn to identify and control.

 

Herb Gottlieb from New York City

(Where our students still have great difficulty explaining experimental errors)
> Tina
>
> Tina Fanetti
> Physics Instructor
> Western Iowa Technical Community College
> 4647 Stone Ave
> Sioux City IA 51102
> 712-274-8733 ext 1429
>

 

 

Herb Gottlieb from New York City
(Where it's nice to live but I wouldn't
want to be a tourist here)
herbgottlieb@juno.com