PHYSICS FOR LIFE SCIENTISTS Week #7 Lab - Parallel and Series Circuits Getting to know the Simulation I. Observing voltage relationships Go to the PHeT web site and use the Circuit Construction Kit simulation (CCK). Drag out three batteries. Measure the voltage of each using the voltmeter and record the voltage in a table like the one shown. Then move the batteries end to end as below to measure combined voltage. Battery Voltage (V) 1 1 2 3 1+2 1+2+3 1+2 1+2+3 Describe the relationship between the number of batteries and the voltage and explain what you think might be happening. b. What could you vary to test your description about the relationship? (Right click on the batteries to change characteristics ) Run several tests recording your data in an organized table. c. Talk to another group about their description, tests and results. Rewrite your description to include the more broad tests. II. Using voltage Use the Circuit Construction Kit simulation to build a circuit with a battery and a light bulb in the Lifelike visual mode. a. Draw what your circuit looks like. b. How does the voltage of the battery compare to the light bulb voltage? Explain what you think is happening. c. Vary the voltage of the battery and write observations about how the brightness is affected by voltage. d. Think about a real light bulb and battery; explain what you think is happening that causes the changes in brightness. III. Using voltage in series circuits Use CCK to build the circuits below with a battery at about 12 volts and light bulbs. Turn on the voltmeter and ammeter to measure voltage of the battery and current into it. Record bulb brightness with descriptive language. Figure 1 Figure 2 Figure 3 # of bulbs Battery Current Brightness voltage into of bulbs battery(A) a Summarize the relationships you observed and explain what you think is happening. b. Test to see if changing the battery voltage causes you to modify any of your conclusions. Explain what you measured and any conclusions you draw from your tests. C. What happens when you take a wire out of a circuit? Explain what you think is happening d. Test using the voltmeter or ammeter in different ways. For example: Does it matter if you take the reading on the left or right of the battery? Switch the meter ends? Describe your tests and results.Building Series and Parallel Circuits I. Series Circuit Construct the circuit figure 1 using The Circuit Construction Kit (CCK) simulation at the PHeT site. Make the resistors have different value and record the value of each resistor. Use the ammeter moving it to take readings in the different places seen in figure 2. Then use the voltmeter to take voltage readings. Calculate R using Ohm's Law (V=IR) for the total resistance in last column. Figure 2 Figure 1 At mmm A1 A2 A3 V2 V3 Resistor Voltage(V) Current (A) Resistance () 1 2 3 Total Vr reading AT reading a. How is the total resistance related to the individual resistances? Total current to the individual currents? Total voltage to the individual voltages? b. Write a paragraph explaining what you think is happening in series circuits to cause the above relationships to occur. (You made a similar circuit with light bulbs using CCK. You may want to experiment with the sim again, keeping in mind that light bulbs are just resistors that glow.).Ill. Combo Circuits I. Put three resistors on the work area. Right click on each to make the resistances different from one another. Make a data table like the one given and record the individual resistances. 2. Build the circuit given in Figure A. Make a table like the one below and complete it by measuring the voltage across each resistor and the power supply and measuring the current through each resistor and the total current coming out the power supply. Resistor lndiviiual Current Vohge Resistance in resistance (amps) {Volts} the circuit oluns ol'ms R=WI 3. Provide evidence that your table information is reasonable. Write down you reasoning and show your calculations. Before you take apart your experiment, show your results to your instructor to see if they are acceptable. Credit is given only if the results are correct and your reasoning is sound 4. Repeat the procedure with the circuit in Figure E. Figure E R1 R2