NAME: Phys 3B - E&M Capacitance Experiment 4: Capacitors in Series and Parallel Circuits The aim of this lab is to measure an unknown capacitance and to confirm the validity of the equations for capacitors connected in series and in parallel. Apparatus: D.C. power supply, Capacitors, Digital Multimeter, 209 resistor and wires. Review Capacitors in parallel have certain characteristics and equation. Fill in the table below. Capacitors share Capacitors have Equation for equivalent capacitance the same .... different .... Parallel Potential Series Charge Charg Leg You will use the above information throughout the lab. Activity 1: Measurement of an Unknown Capacitor WA 220 1. Set up the circuit shown in figure 1. A connection gui C is available to assist you in setting up the circuit. Capacitor C is known and C1 is unknown. Record the known value of C in table 1. figure 1 2. Make sure that the voltmeter is set on "DC volts" throughout this experiment. The power supply voltage is in the range 0 to 25 volts, so start out with the meter set on a scale that wil accommodate this range. It is best to set the meter on a high range at first until you know approximately what voltages you are dealing with. Measure the battery voltage. Record it in table 1 as VB.Phys 3B - E&M Capacitance Experiment 4: Capacitors in Series and Parallel Circuits 3. Let the capacitors charge for a few seconds, then close switch S and immediately read V. You must observe the initial reading of V because the voltmeter has a finite resistance and begins to discharge C1 so that the reading falls. Record your results in table 1. 4. You can solve for the unknown capacitance. The battery voltage is the sum of the voltages on each capacitor: VB = Vc + VC1 (1) The voltage across any capacitor is V = = = C = Q (2) VCI Using the above equations solve for the C, in terms of VC,, VB, and your known capacitance, C. ( = Q C1= 4 - Q= CIVCI VCi VC ( = LIVE - VB = C . CIVelt VC,= CI = ( UB- Veilc VCI 5. Using your derived equation compute C1 and record the result in table 1. Repeat the procedure two more times, then enter the average value of C1 in table 1. Between trials it is necessary to disconnect the capacitors from the circuit and discharge them by placing a clip lead directly across their terminals for several seconds. Repeat the entire procedure for the other unknown capacitor C2. Calculate the percent difference for each capacitor using the 71 X 10 average value and the accepted value. The accepted value can be found on the capacitor. VB = LOV C= 10 MF Manufacturer Experimental Average % Value Value Value Difference C1 47 MF 1.657 T. bbv C2 100 MF 10 . 9 6 V 0 . 94 V 0. 93 V Table 1 Activity 2: Capacitors in Series and in Parallel:lys 3B - E&M Capacitance xperiment 4: Capacitors in Series and Parallel Circuits 1. In place of C1 in figure 1, place Ci and C2 in series as shown in figure 2. Use the handouts from class to guide you in making the connections. 2. Measure the capacitance by the procedure following in Activity 1. Record data in table 2. 3. Repeat using C1 and C2 connected in parallel as in figure 3. 4. Record all data in tables 1 and 2 Complete the necessary calculations and record the results in tables land 2. WA 220 C C C C2 figure 3 figure 2 V Experimental Average Calculated % Value Value Value Difference Series 203V to 3 V Parallel 0 . 6 4 2 O. 6 3 9 V Table 2 nalysis of DataPhys 3B - E&M Capacitance xperiment 4: Capacitors in Series and Parallel Circuits 1. Calculate the equivalent capacitance for C, and C2 connected in series and in parallel using average experimental values in table 1. Record your results in table 2 under "Calculated Values". Calculate the % difference between the average experimental value and the calculated value. Show work below. % Difference = Calculated-Experiementall Calculated+Experimental 2 2. Discuss sources of error in your conclusion