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Ohm’s Law in series and parallel circuits -- Lab CLASS SET – WRITE ON YOUR OWN PAPER Each individual of a lab group will be writing down data collected so it can be taken to the computer lab, graphed, and analyzed. You will be constructing 1 resistor, 2 resistor, and 3 resistor series circuits using 1, 2, and 3 D Batteries for each. As a reminder: a. Testing voltage: Leads from multimeter on either side of a battery or multiple batteries in a closed circuit (use the 20 DC Volts setting on multimeter). b. Testing current: Leads from multimeter closing an open circuit, so electricity flows through the multimeter (use the 200 mAmp DC setting on the multimeter). c. Testing resistance: Leads on either side of the resistor in an open circuit (use the 200Ω setting on the multimeter) In the following data table R1 = blue resistor, R2 = Red Resistor, and R3 = Green resistor. The three places for voltage are for one, two, and three batteries. Construct this data table on your own paper and take the following data: 1 resistor series R1 = ____ Ohms 2 resistor series R1 = ____ Ohms R2 = ____ Ohms Voltage (Volts) Voltage (Volts) Current(Amps) Current(Amps) 3 resistor series R1 = ____ Ohms R2 = ____ Ohms R3 = ____ Ohms Voltage(Volts) Current(Amps) ≈1.5 (record actual) ≈1.5 (record actual) ≈1.5 (record actual) ≈3 (record actual) ≈3 (record actual) ≈3 (record actual) ≈4.5 (record actual) ≈4.5 (record actual) ≈4.5 (record actual) Take this data to the computer lab and graph the three sets of data on an Excel Spreadsheet (three sets of data on one graph). Graph voltage on the Y-axis and current on the X-axis. After you have the three sets of data graphed: Right click (or Ctrl click) on the data set and select “Add Trendline” which will give you a line of best fit for that data set. Select “Show equation on chart.” Record the slope intercept form of the linear equation for your data on your paper for each of the three circuits underneath the data table 1 bulb ---- y= mx + b 2 bulb ----- y = mx + b 3 bulb ----- y= mx + b Now, you get to think about your data and record your thoughts. On your lab title this section “SERIES CIRCUIT DATA ANALYSIS” and answer the following questions: What do you notice about the slope of your line and the resistance in your circuit? Does this make sense with regard to Ohm’s Law (if you have not read about Ohm’s law yet for the homework then you can research it online right now)? Why or why not – explain your reasoning? PARALLEL CIRCUITS You will be constructing 2 bulb, 3 bulb, and 4 bulb parallel circuits using 1, 2, and 3 9 V Batteries using an online simulation (http://phet.colorado.edu/en/simulation/circuit-construction-kit-ac) linked from the class website. R1, R2, R3, and R4 refer to the first, second, third, and fourth bulbs in the parallel circuit. You will be measuring the current AS IT LEAVES THE BATTERY using the non-contact ammeter on the simulation. Construct this data table on your own paper and take the following data: 2 bulb parallel R1 = ____ Ohms 3 bulb parallel R2 = ____ Ohms Voltage (Volts) 9.00 18.00 27.00 Current(Amps) Voltage (Volts) 9.00 18.00 27.00 R1 = ____ Ohms R2 = ____ Ohms R3 = ____ Ohms Current(Amps) 4 bulb parallel R1 = ____ Ohms R2 = ____ Ohms R3 = ____ Ohms R4 = ____ Ohms Voltage(Volts) Current(Amps) 9.00 18.00 27.00 Graph the three sets of data on an Excel Spreadsheet (three sets of data on one graph). Graph voltage on the Y-axis and current on the X-axis. After you have the three sets of data graphed: Right click (or Ctrl click) on the data set and select “Add Trendline” which will give you a line of best fit for that data set. Select “Show equation on chart.” Record the slope intercept form of the linear equation for your data on your paper for each of the three circuits below the data table. 2 bulb ---- y= mx + b 3 bulb ----- y = mx + b 4 bulb ----- y= mx + b BIG HINT: In a parallel circuit the total resistance in the circuit can be found with the following equation: 1/Rtotal = 1/R1 + 1/R2 + 1/R3 + 1/R4 … Now, you get to think about your data and record your thoughts. On your lab title this section “PARALLEL CIRCUIT DATA ANALYSIS” and answer the following questions: What do you notice about the slope of your line and the resistance in your circuit? Does this make sense with regard to Ohm’s Law? Why or why not – explain your reasoning?
