# Day 158: R in S and P

Advanced Physics:

That stands for Resistances in Series and Parallel.  This is usually one of my favorite experiments.  It is easy to gather the data and the results are always spot on. The experiment graphically develops the equations for resistance sin series (Rt=R1+R2+R3…) and parallel (1/Rt = 1/R1 + 1/R2 + ….) But… this year, thee was just no time to do it.  Here is the way we usually completed it.  It is patterned after an article i read in The Science Teacher a number of years ago.

We use a set of about a dozen fixed resistors with an ohmmeter and a Pasco Circuit board.  Very simply, the students measure the resistance value of each individual resistor, the pick one to hold constant. They wire the remaining resistors (one at a time) in series and measure the total resistance. They plot total resistance vs. resistor 2.  Here is a picture and some sample data:

And the parallel…

But, as mentioned, not time left to do it this year, so we just developed it qualitatively with the spools:

After a schematic circuit diagram assessment, we will practice simplifying a complex circuit, .  More on that tomorrow.

General Physics:

We finished the Mystery Boxes activity and then practiced a bit for a schematic diagram assessment tomorrow also.  We then had a short pre-lab discussion for the Ohm’s Law experiment.

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