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UNT PHYS 2240 Lab SPRING 2021 - Alymjan Rejepov/Experiment 4: Series and Parallel Circuits/Experiment
Assignment # 4B Name Lab 4 Experiment I worked in a group with
Evan Hathaway - Jun 30, 2020, 11:22 AM CDT
Update and Submit
Equipment
Content LA Thirteen - Jun 11, 2020, 11:06 PM CDT
1 AC/DC Electronics Laboratory EM-8656
1 Set of circuit components
1 Digital Storage Oscilloscope TBS-1052
2 Oscilloscope Probes
1 Digital Multimeter EX 330
1 DC Power Supply TP3005T
Content LA Thirteen - Jun 11, 2020, 11:06 PM CDT
Resistor Check
Content LA Thirteen - Jun 11, 2020, 11:06 PM CDT
To properly analyze circuits and series and parallel, we should know the actual resistance values of each resistor being used. In other words, recall that each resistor’s resistance value can fall within an acceptable tolerance range, denoted by the usually gold (+/- 5%) or silver (+/- 10%) band. We should then first measure each resistor with our digital multimeter.
1. Locate the six resistors needed: 2x 100 Ω, 2x 330 Ω, and 2x 560 Ω resistors.
2. Begin by using the DMM to measure each resistor. Make sure the meter is set to measure resistance, and record each resistance value in Table 1 below.
Table 1: Measured Resistor Values
R1 = 330 Ω R2 = 560 Ω R3 = 100 Ω R4 = 100 Ω R5 = 560 Ω R6 = 330 Ω
Content LA Thirteen - Jun 11, 2020, 11:09 PM CDT
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Procedure A: Series and Parallel Resistor Circuits
Content LA Thirteen - Jun 11, 2020, 11:10 PM CDT
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Figure 4: The digital multimeter is inserted in series with the power supply to determine the current provided by the source. The “A” symbol refers to ammeter, which is the DMM in current sensing mode. Note: it does not matter with which terminal (+ or -) the DMM is placed in series, since the current entering the circuit must equal the current leaving the circuit. This will be the concept of Lab 6 (Kirchhoff’s Laws).
In this experiment, we must measure the total current being provided to each circuit, which is directly being supplied by the DC Power supply. Therefore, we will use the digital multimeter in current sensing mode, i.e., as an ammeter, to measure the current before it arrives to the circuit, as shown in Figure 4.
1. Construct the first circuit shown in Circuit Diagram 1 (Fig 3).
2. As shown in Figure 4, insert the digital multimeter in series with the DC power supply. Doing this will directly (and accurately) measure the current provided to the entire circuit by the power supply.
Use banana plugs for this connection, rather than the normal DMM probes.
3. Set the DMM to be on the milliampere scale by turning the dial to “mA.”
4. DO NOT connect the power supply to the circuit yet.
5. Turn on the DC power supply. Verify both voltage and current are set to zero by doing the following
a. Press the Voltage knob and set to 0.000 Volts.
b. Press the Current knob and set to 0.000 Amps.
6. Connect the power supply / DMM combo to your circuit.
7. Set Voltage on the DC power supply to 15.00 V
8. SLOWLY increase the current in increments of 0.010 A until 15.00 V has been reached on the power supply. For the first circuit, only about 0.020 A or 0.030 A should be needed. Once the current has been adjusted, you will notice it decreases slightly, such that 15.00 V is sustained.
9. After the reading stabilizes, record the current being measured by the DMM in Table 2 below.
10. Set the current to 0.000 A on the DC power supply.
11. TURN OFF the DC power supply.
12. Calculate the theoretical equivalent resistance Req for the circuit by using equations 2 and 3. Enter this value in Table 2. Use the measured
values of each resistor for this step.
13. Compute the measured equivalent resistance Req by applying Ohm’s law: where
V = 15 Volts and I is equal to the measured current found previously in step 9. Enter this value in Table 2.
14. Compare the theoretical and measured equivalent resistances by calculating the percent difference between the two, and enter the result in Table 2.
15. Disassemble circuit 1, construct circuit 2, turn on the DC power supply, and repeat steps 8-14 for circuit 2.
16. Repeat step 15 for circuits 3 and 4.
17. Set the current and voltage on the DC power supply both to 0.000 V and 0.000 A.
Table 2: Resistance Values
Content LA Thirteen - Jun 11, 2020, 11:28 PM CDT
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Circuit Diagram Theoretical Req
(Ω) Measured
Current (mA) Measured Req (Ω)
Percent Difference
1
2
3
4
Procedure B: Series and Parallel Lightbulb Circuits
Content LA Thirteen - Jun 11, 2020, 11:29 PM CDT
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Just as in the previous section, here you will measure each lightbulb’s resistance individually, then use them to construct series/parallel combinations and measure the equivalent resistance of these combinations. As you previously discovered in the Ohm’s Law lab, the resistance of the lightbulbs is not constant.
In this experiment, we will not need an ammeter to measure the current provided by the power supply. The reason for this is that the current being drawn by the lightbulbs is much larger than with the resistors. In general, the resistance of the bulbs is much less than the resistors used in the previous section. Hence, we will read the current and voltage directly off the power supply.
1. Connect lightbulb A in series directly to the power supply, as shown in Figure 5.
2. Turn on the DC power supply. The current and voltage should be zero from the previous experiment. Set the voltage to 2.00 V
3. SLOWLY increase the current in increments of 0.010 A (10 mA) to reach the 2.00 V. This should be about 0.260 A for the specific lightbulbs being used.
4. Calculate the resistance of bulb A with these parameters, using , using the voltage and current as displayed by the power supply. Record the value in Table 3 below.
5. Decrease the current to zero.
6. Repeat steps 3-5 for lightbulbs B and C.
7. Make sure the current is set to zero. Place bulbs A & B in series as shown in Figure 6.
8. Repeat steps 3-5.
9. Make sure the current is set to zero. Place bulbs A & B in parallel as shown in Figure 7
10. Repeat steps 3-5.
11. Make sure the current is set to zero. Place bulb A in series with bulbs B & C which are in parallel as shown in Figure 8.
12. Repeat steps 3-5.
Table 3. Lightbulb circuit resistance values
Bulb System Measured Resistance
(Ω)
A
B
C
A&B Series
A&B Parallel
Series Parallel
Content LA Thirteen - Jun 11, 2020, 11:40 PM CDT
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Conclusions
Content LA Thirteen - Jun 11, 2020, 11:41 PM CDT
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Series and Parallel Circuits
1. How well did the theoretical values compare to the experimental values?
2. What are sources of error in this experiment, and how could they be minimized?
Light Bulb
3. How does the brightness of two bulbs in series compare to a single bulb? Explain this in terms of power.
4. How does the brightness of two bulbs in parallel compare to a single bulb? Explain your answer.
5. Explain what is happening in the series parallel setup.
Content LA Thirteen - Jun 11, 2020, 11:43 PM CDT