Day 145: More on the Fel Lab and the BigBlueButton

Advanced Physics:

We just finished day one of the post lab discussion for the electrostatic force experiment (well, simulation).  A bit more detail on how I set it up.  Not only am I using this to build the model for Coulomb’s Law, Ia m also using it as a launching point for discussing the electric field. Here’s how. As we completed the pre-lab discussion, we agreed that when we looked at the relationship between the force and charge, we could only change the charge on on object, so we had to keep the charge on #1 constant as well as the distance separating the two.  When I set it up I,  assigned the constants such that we could look at the slope value for the electrostatic force as a function of charge would allow us to look at the characteristics of the Electric Field strength. Here is the handout ( Electrical Force Simulation(13-14) )and in the box, is how I used playing cards to set the constants and the field strength. Notice  there are two groups that have the same distance but multiples of the charge, and groups that have the same charge, but multiples of the distance.  This allows us to see how the slope (later to be defined as the electric field strength) is affected by the charge establishing the field, and by the distance away from the charge the test charge (q2 in this case) is placed. So here are the graphs:

Screen Shot 2015-04-23 at 9.41.36 PM


Screen Shot 2015-04-23 at 9.44.25 PM

This one provides a nice chance to discuss the difference between an inverse relationship and an inverse square relationship.  For some kids, the first graph in this series in inverse.

So now we have three relationships:  Fel proportional to q1; Fel proportional to q2; and Fel proportional to inverse square of distance (1/d^2). We want all three in one  Fel proportional to q1q2/d^2 and we want an equation for the electric force. So to change the proportional to an equal sign, we need the proportionality constant (or slope) of that graph Fel vs q1q2/d^2. Here is it:

Screen Shot 2015-04-23 at 9.45.14 PM

I think you recognize the slope!



The BigBlueButton

Some of you may already know about the BigBlueButton Conference app.  It is hosted in Schoology which the incredibly awesome LMS our district has bought into. The BigBlueButton app allows you to video conference with your students.  You can also limit it to just audio or mute the mic and go all typing. It allows you to upload a pdf and the annotate as your heart desires.  It even allows the session to be recorded.   I just used it for the last two night with my CAPP kids that were working on a rather challenging set of momentum-impulse problems that are due tomorrow. It is really sweet watching/listening as the students ask questions and answer each others.  Talk about fostering collaboration and communication… those of us that are required to complete the Educator Effectiveness Project are all set.

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