Phys 102 formal simple dc circuits lab report
- 1. Kaitlyn Greiner Formal Lab Report: Title of Experiment: Simple dc Circuits Date Performed: July 16th, 2014 Lab Partners: Erin Phlegar and Stephen Few Physics 102L, Section: 02 Professor Teklu Abstract: In this lab, my objective was to understand the relationships between resistance, potential difference, and current in a simple circuit. To accomplish this, we built a series and parallel circuit each containing three resistors. We measured the current and potential differences across the resistors on each circuit. I learned that, in a series circuit, the current remains the same throughout the circuit and the potential difference varies across each resistor. In a parallel circuit, the current varies across each resistor and the potential difference remains the same throughout the circuit.
- 2. Introduction: In this experiment, we are investigating the relationships between resistance, potential difference, and current in a simple circuit. We are going to learn how to build simple circuits. We are going to build both a series and parallel circuit. Before obtaining our measurements, we expect to find that the current will remain the same and the potential difference values will vary across the resistors of the series circuit. We expect to find that the opposite is true for the parallel circuit. We think that the values for current across each resistor will vary from each other and that the potential difference value will be the same across the circuit. Description of Apparatus: To build our series circuit, we connected a power supply to three different resistors using clips and wires. The resistors were lined up all next to each other. A voltmeter was used to obtain our measurements. We placed the two leads of the voltmeter on each side of each resistor and the power supply to obtain our voltage values and current values. Our series circuit looked like the one in the sketch below: To build our parallel circuit, we connected a power supply to three different resistors in parallel using wires and clips. The three resistors were more vertically stacked than in a line. A voltmeter was used to obtain our measurements for this circuit as well. Two leads of the voltmeter were placed on each side of each resistor and the power supply to obtain voltage and current values. Our parallel circuit looked like the one in the sketch below:
- 3. Procedure: We first built our series circuit. We set up a series circuit with three resistors to determine how resistors affect current and voltage. We measured the current and voltage of each resistor. To measure the voltage, we placed the two leads of the voltmeter on either side of each resistor and across the power supply and recorded the value for each. We then added the voltages at each resistor together to get the measured voltage value. We measured current in same way but we switched to amps instead of voltage when measuring. We recorded this value as our measured current. We then calculated the current and voltage for the series circuit. We used four volts as our set voltage value and added the three resistances together for our equivalent resistance value. We plugged these values into this equation, I= ΔV/Req, to calculate our current. Lastly, we calculated an overall percent error for our measured and calculated current and voltage for the series circuit. Next we built our parallel circuit. We set up a parallel circuit with three resistors to determine how resistors affect current and voltage. We measured the current and voltage of each resistor. To measure the voltage, we placed the two leads of the voltmeter on either side of each resistor and across the power supply and recorded the value for each. We recorded this value as our measured voltage. We measured current in same way but we switched to amps instead of voltage when measuring. We then added the current at each resistor together and recorded this value as our measured current. We then calculated the current and voltage for the series circuit. We used four volts as our set voltage value and added the inverse of the three resistances together to find the equivalent resistance value (1/Req=1/R1 +1/R2 + 1/R3). We plugged these values into this equation, I= ΔV/Req, to calculate our current. Lastly, we calculated an overall percent error for our measured and calculated current and voltage for the parallel circuit. Results: Series Circuit: Calculations: R1=1kΩ R2=2.2kΩ R3=3.3kΩ R1+R2+R3=6.5kΩ 6500Ω 1+2.2+3.3=6.5
- 4. Req=6500Ω Voltage: 4V I= ΔV/Req I=4/6500 I=6.15x10^-4 A Current is always the same number throughout a series circuit. Calculated Current: 6.15x10^-4 A MeasuredCurrent: 6.10x10^-4 A I1=I2=I3=6.10x10^-4 A % Error: (calculated-measured)/calculated x100 (((6.15x10^-4)-(6.10x10^-4))/(6.15x10^-4)) x100 = .813% % Error for Current: .813% Voltage is not the same number throughout a series circuit. Calculated Voltage: 4 V MeasuredVoltage=3.993 V V1=.603 V2=1.363 V3=2.027 V1+V2+V3=V .603+1.363+2.027=3.993 V % Error for Voltage: .175% ((4-3.993)/4) x100= .175% Data Tables: I1 (A) I2 (A) I3 (A) I (A) Overall Measured 6.10x10^-4 A 6.10x10^-4 A 6.10x10^-4 A 6.10x10^-4 A Calculated 6.15x10^-4 A 6.15x10^-4 A 6.15x10^-4 A 6.15x10^-4 A Experimental Error % .813%
- 5. V1 (V) V2 (V) V3 (V) V (V) Overall Measured .603 1.363 2.027 3.993 Calculated 4 V 4 V 4 V 4 V Experimental Error % .175% Parallel Circuit: Calculations: Voltage: 4V I= ΔV/Req 1/Req=1/R1 +1/R2 + 1/R3 Current is not the same number throughout a parallel circuit. I1= V1/R1 I1=4/1000 I1=.004 I2=V2/R2 I2=4/2200 I2=.0018 I3=V3/R3 I3=4/3300 I3=.0012 I1+I2+I3= I .004+.0018+.0012=.007 Calculated Current: .007 MeasuredCurrent: .00702 I1=.00120 I2=.00179 I3=.00403 .00120+.00179+.00403=.00702 % Error for Current: .286% ((.007-.00702)/.007) x100= .286% Voltage is the same number throughout a parallel circuit. Calculated Voltage: 4V
- 6. MeasuredVoltage: 3.98V V1=V2=V3=3.98V % Error for Voltage: .5% ((4-3.98)/4) x100= .5% Data Tables: I1 (A) I2 (A) I3 (A) I (A) Overall Measured .00120 .00179 .00403 .00702 Calculated .004 .0018 .0012 .007 Experimental Error % .286% V1 (V) V2 (V) V3 (V) V (V) Overall Measured 3.98V 3.98V 3.98V 3.98V Calculated 4V 4V 4V 4V Experimental Error % .5% Conclusions: In the series circuit, the current across each resistor is the same number throughout the circuit (I1=I2=I3). Any charge that flows through one resistor also flows through the other. The measured voltage across each resistor varied. V1, V2, and V3 were different values. The sum of these potential differences is equal to the total potential difference across the circuit. The equivalent resistance of a series circuit is the sum of each resistance. If one part of this circuit failed, none of the other parts would work either. The low percent error for current shows that this formula, I= ΔV/Req, is accurate. Both percent errors were very low. This means that very little mistake was made during the experiment for the series circuit. In the parallel circuit, the current across each resistor was not the same number throughout the circuit. The values for I1, I2, and I3 were different. The current that enters a point must be equal to the total current leaving the point. Therefore, the overall current is the sum of each individual current. The voltage across each resistor was the same number throughout the circuit (V1=V2=V3). The values are the same because each resistor is connected directly across the battery terminals. The equivalent resistance of a parallel circuit is the sum of the inverses of each resistance (1/Req=1/R1 +1/R2 + 1/R3). The percent errors for current and voltage are very low. This means that very little mistake was made during the experiment for the parallel circuit.