Experiment No. 306: Series and Parallel Circuits Raagas, Michelle Mae G. School of Chemical Engineering, Chemistry, Biological Engineering and Material Science Engineering Mapua Institute of Technology, 658 Muralla St., Intramuros, Manila City, Philippines [email protected]
OBJECTIVE Series and parallel circuits have different behavior. This experiment aims to determine the voltage through each resistors and the current flowing on a series circuit and parallel circuit. In addition, it also aims to find out the circuit’s total current flow for the both series and parallel by the use of multi meter and compare the two. Another purpose of this experiment is to study the relationship of the voltages and current flowing through each resistors and its total voltage and current using the concept of ohm’s law.
On this experiment, we will be observing two types of circuit, the parallel and the series one. For the first part of the experiment, the series circuit will be done. First, set the resistor to the values given by your Professor, in our group, we are given the value of 88, 108, and 128 ohms. You need to set the resistor first before connecting the wire to avoid the discharging of the battery. Then, align the resistors horizontally and connect them together to produce a series connection. Also, connect the battery the same way the resistors are connected. See figure below.
METHODOLOGY We will be needing the materials below to acquire data that we will need later for the computations. See figure 1
Figure 2. the set-up for the series connection
Figure 1. Materials needed (3 pcs. Resistance boxes, 3 pcs. 1.2 V baterries, 12 pcs. Connecting wires, VOM, Ammeter)
After that, measure its current flow through each resistor by the use of multi meter . Also, get the total current by connecting the VOM on the resistor 1 and battery 1. To check, the total current must be equal to each of the current of the three resistor. Then, identify the voltage in each resistor and it’s sum
shoud be equal to the voltage that is taken by connecting the multimeter to first and third battery. For the part two which is the parallel connection, the resistors were aligned vertically or parallel to each other. See figure below
Figure 3. Set-up for parallel connection Unlike on the series connection, only the resistor 1 is connected to the batteries. Get the current flowing from resistor 1 by connecting the second resistor and the battery 1 to the multi meter. Same thing is to be done to identify the current flowing through second and third resistor. Again, get the total current flow and it must be equal to the summation of the three. Lastly, identify the voltage and it should be equal to each other and to the total voltage. After you gather all the experimental data needed, you are now able to measure the computed values.
DATA and SAMPLE COMPUTATIONS Table 1.A Resistance 1 (𝑅1 ) = 88 Ω Resistance 2 (𝑅2 ) = 108 Ω Resistance 3 (𝑅3 ) = 128 Ω Total Resistance (𝑅𝑇 ) = 324 Ω Total Voltage (𝑉𝐷𝐴 ) = 3.66 V Table 1.B Series Circuit Experimental Computed 0.9064 V Voltage across 𝑅1 0.907 V (𝑉𝐴𝐵 ) 1.115 V 1.1124 V Voltage across 𝐶 (𝑉𝐵𝐶 ) 1.32 V 1.3184 V Voltage across 𝑅3 (𝑉𝐶𝐷 ) Current flowing 0.011 A 0.0103 A through 𝑅1 (𝐼𝐵 ) Current flowing 0.011 A 0.0103 A through 𝑅2 (𝐼𝐶 ) Current flowing 0.011 A 0.0103 A through 𝑅3 (𝐼𝐷 ) 0.011 A 0.0103 A Total current (𝐼𝐴 ) % Difference 6.57 % Total Resistance = 88 + 108 + 128 = 324 Ω 𝐼=
𝑉 0.907 = = 0.0103 𝑅 88
𝑉 = 𝐼𝑅 = (0.0103)(88) = 0.9064 % 𝑑𝑖𝑓𝑓 = |
𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 − 𝑐𝑜𝑚𝑝𝑢𝑡𝑒𝑑 | 𝑥100 𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 + 𝑐𝑜𝑚𝑝𝑢𝑡𝑒𝑑 2
0.011 − 0.0103 | 𝑥100 0.011 + 0.0103 2
= 6.57 % Figure 4.a series connection setup 4.b parallel connection set-up
Graph of series circuits
R Vs. V graph 0.00015
Table 1.B Parallel Circuit Experimental Computed 3.54 V 3.52 V Voltage across 𝑅1 (𝑉𝐴𝐵 ) 3.55 V 3.564 V Voltage across 𝐶 (𝑉𝐴𝐶 ) 3.85 V 3.584 V Voltage across 𝑅3 (𝑉𝐴𝐷 ) Current flowing 0.037 A 0.04 A through 𝑅1 (𝐼𝐵 ) Current flowing 0.03 A 0.033 A through 𝑅2 (𝐼𝐶 ) Current flowing 0.026 A 0.028 A through 𝑅3 (𝐼𝐷 ) 0.1 A 0.101 A Total current (𝐼𝐴 ) % Difference 1%
0.0001 0.00005 0 88
Graph of parallel circuits
R and I graph Current
Table 2.A Resistance 1 (𝑅1 ) = 88 Ω Resistance 2 (𝑅2 ) = 108 Ω Resistance 3 (𝑅3 ) = 128 Ω Total Resistance (𝑅𝑇 ) = 35.1674 Ω Total Voltage (𝑉𝐸𝐴 ) = 3.55 V
500 400 300 200 100 0 88
Total resistance = (88 + 108 + 128) = 35.1674 𝐼=
𝑉 3.54 = = 0.04 𝑅 88
𝑉 = 𝐼𝑅 = (0.04)(88) = 3.54 𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 − 𝑐𝑜𝑚𝑝𝑢𝑡𝑒𝑑 % 𝑑𝑖𝑓𝑓 = | | 𝑥100 𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 + 𝑐𝑜𝑚𝑝𝑢𝑡𝑒𝑑 2 =|
0.1 − 0.101 | 𝑥100 0.1 + 0.101 2
ANALYSIS OF DATA On the first part, since the resistors are connected in series, there is only one current flow throughout the resistors which is observed as we notice that the current flow on three different resistor is the same and also its total current. Also, its total voltage is the sum of the voltages across the resistors. On the other hand, by performing the parallel connection, the one that is constant are the voltages and the total current flow is the sum of the three current flow from different resistors. There are some errors that you may encounter, as I said earlier, do not connect your circuit to the power source while you are assembling them. In addition, make sure that the knob of the multi meter is in the voltage selection when measuring voltage and in current selection when measuring current.
CONCLUSION By performing this, the objectives of the experiment was achieved. We are able to determine the voltage through each resistors and the current flowing on a series circuit and parallel circuit. In addition, we are also able to investigate the relationship of the voltages and current flowing through each resistors and its total voltage and current using the concept of ohm’s law. The ohm’s law which states that the voltage is proportional to the current flow and to the resistance which is proven in this experiment. The current flow is expected to be uniform throughout the series circuits. Therefore, by applying the ohm’s law, we observe that as the resistance increases, the voltage decreases. Then again, in parallel connection, the voltages is expected to be uniform thus, we notice that as the resistance is increasing, the current flow is increasing as well. ACKNOWLEDGMENT I would like to thank Sir Ricardo De Leon for teaching us the process on what to do because it is confusing for us on where to connect the wires. Thank you for guiding us throughout the experiment. Moreover, I would also like to thank my groupmates for having such a great role in this experiment. All of us are participating and contributing. In addition, I would like to recognize their calmness, they did not take the pressure, else, they make this experiment memorable and fun to do. Lastly, I would like to thank the two laboratory assistant for explaining how to handle and use properly the equipment. REFERENCES  Taylor, C. (2003). Voltage, Current, Resistance, and Ohm's Law  Kuphaldt, T. R. (1999). Lessons in Electric Circuits. Design Science License.