DL-Circuits

Demo - Ohm's Law - I connect a light bulb to a power supply in series with a slide wire rheostat.  I show the effect of more and less Voltage (Voltage like pressure) and the effect of more and less resistance.

Demo - Three Light Bulbs - Given the circuit diagram, the students predict the effect of turning on light bulb 3 on the brightness of light bulb 1 and 2.  I have them vote and raise their hand.


Lab - stuff

Lab - Resistance of a wire.  Students gather Current vs Voltage data for a piece of NiChrome wire.  They make a graph with generous error bars, and put a linear model through it.  Then they estimate the uncertainty of the slope by putting min and max slope lines through the data.  This data is Ohmic - constant slope, 0 y intercept.

Like this: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/currents-and-circuits/resistance-of-a-wire

or like this: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/graphing-prelab



Lab - Light Bulb and Diode.  Students gather Current vs Voltage data for a light bulb just as it is getting hot, and a diode just as it is letting current flow.  These graphs are very non-ohmic.  The light bulb is a beautiful downwardly concave graph of I vs V.  The Diode is nominally linear, but has a huge negative y intercept.

I have the students use best fit lines to find the differential resistance on the graphs.

Help site: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/currents-and-circuits/light-bulb-and-diode-lab

Lab - Internal Resistance of a Battery.  Students gather Voltage vs Current data for a battery under various loads (currents).  As the current increases, the terminal voltage of the battery decreases, and they use this to determine the internal resistance of the battery.  

Help site: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/currents-and-circuits/internal-resistance-of-a-battery-lab


Lab - I do this as a station lab.

Oscilloscope Lab Part 1 - and old fashioned CRT Oscilloscope.  Students look at the output of a transformer (about 6 V output) and determine the peak voltage  of the waveform, and the period.  From this they calculate the RMS voltage, and the Frequency of the waveform (about 60 Hz)

 Oscilloscope Lab Part 2 - A $14k Tektronix prototype donated by parent Devin Bingham.  Students analyze the input and the output of a full wave bridge rectifier.  See the handout.  It's pretty cool.

Help Site: https://sites.google.com/a/ttsd.k12.or.us/tuhsphysics/home/htp-ib-physics/currents-and-circuits/oscilloscope-lab