Marissa's+Resistive+Circuits+Lab

=Resistive Circuits Lab=

Date: 2/7/2010


 * Participants**: Marissa Marton


 * Purpose**: The purpose of this lab was help the students understand the behavior of current and voltage by constructing a series of circuits in class. Observations and data collection were vital in this process of understanding. By looking closely at these components in the Resistive Circuits Lab, the class was able to see a connection between voltage, current, and resistance.


 * Brief Description of Experiment**: In this experiment, the class constructed circuits in order to understand how voltage, current, and resistance are all connected and function as a whole. We first did this by creating circuits via a simulation. With this simulation, we were first able to play around with it and get a narrow understanding of what a circuit is and how it works. We then did the same process of building circuits, only we had real materials to work with in class (e.g resistors, power supplies, voltmeters, ammeter, light bulbs…). This gave the class a deeper understanding of how circuits function because we had to build them ourselves, take data, and overall observe how the multiple circuits that we built created patterns and showed interesting connections. The types of circuits that we built include the following: basic circuit with only one resistor, circuit containing a light bulb, three resistors in series, three resistors in parallel, and finally a type of circuit that had four resistors total in both series and parallel. After we collected data from the experiment with using real circuits, we went back to the simulation to compare our results with more accurate figures. We were then able to notice interesting patterns within some of the different circuits.


 * Data**:

__Measuring the Resistance of a Resistor (Activity # 1) Graph / Chart Explanation__: ** For Measuring the Resistance of a Resistor (Activity # 1) the graph depicts that as the voltage is increased, the current also increases in correlation. Since resistance equals voltage divided by current, the greater the value of the voltage, the greater the resistance will be as well. Also, with a lower voltage and higher current, the resistance would decrease in value. For the chart, each student had to calculate the resistance (last column of the chart titled Resistance in Ohms) and this was done by the equation ** R = V / I (resistance equals voltage divided by current). In addition, the resistance calculated from the graph is 8.576 Ohms. This was done by the slope equaling 1 divided by the resistance (m = 1 / R).

//Measuring the Resistance of a Resistor (Activity # 1) Graph//:

//Measuring the Resistance of a Resistor (Activity # 1) Chart//: Resistance from graph: 8.576 Ohms
 * **Battery Voltage (V)** || **Resistor Voltage (V)** || **Current (Amps)** || **Resistance (Ohms)** ||
 * 20 || 20.7 || 2.3 || 9 ||
 * 16 || 16.7 || 1.8 || 9.28 ||
 * 4 || 4.4 || 0.4 || 11 ||
 * 7 || 7.7 || 0.8 || 9.625 ||
 * 13 || 13.8 || 1.5 || 9.2 ||
 * 8 || 8.77 || 0.9 || 9.74 ||
 * 2 || 2.05 || 0.1 || 20.5 ||

__A non-Ohmic Device (Activity # 2) Graph / Chart Explanation__: For A non-Ohmic Device (Activity # 2) the graph also depicts that ** as the battery voltage is increased, the current also increases in correlation. In addition, the resistance also increases with an increase in voltage. The same explanation as the one for Measuring the Resistance of a Resistor (Activity # 1) applies here as well. The same calculations as described in Activity # 1’s explanation also applies here. A difference for the non-Ohmic device experiment is that the battery voltage used was much lower than that of measuring the resistance of a resistor. This is because the light bulb was being utilized for this activity and a requiremetnt was not to go past .30 A. However, the same pattern is still seen. **

//A non-Ohmic Device (Activity # 2) Graph//: //A non-Ohmic Device (Activity # 2) Chart//: Resistance from graph: 18.9 Ohms
 * **Battery Voltage (V)** || **Resistor Voltage (V)** || **Current (Amps)** || **Resistance (Ohms)** ||
 * 0 || 0.30 || 0.10 || 3 ||
 * .2 || 0.51 || 0.11 || 4.636 ||
 * .4 || 0.82 || 0.14 || 5.857 ||
 * .9 || 1.31 || 0.17 || 7.706 ||
 * 1 || 1.54 || 0.19 || 8.105 ||
 * 1.1 || 1.70 || 0.20 || 8.5 ||
 * 4 || 4.96 || 0.35 || 14.171 ||

I = V / R…(Current = Voltage / Resistance) || R = V / I…(Resistance = Voltage / Current) || m = 1 / R…( Slope = 1 / Resistance) ||
 * Sample Calculations:**
 * //Current Calculation// || The current (amps) is calculated by dividing voltage (volts) by resistance (ohms).
 * //Resistance Calculation// || The equation can be rearranged in such a way so that the resistance (ohms) can be determined. One does this by dividing voltage (volts) by current (amps).
 * //Slope Claculation// || Another important concept to keep in mind is that the slope of a line on a Current versus Voltage graph is equal to one divided by resistance (ohms).

Overall, I learned from this lab about how current and voltage function within a circuit. I also learned how to build interesting circuits and I got to see how resistance ties into the process of a complete and fully functional circuit. The patterns involved were also interesting and seeing the way the patterns work and understanding how they form was beneficial.
 * Results**:


 * Lab Questions**:

// Part 1: You should include a graph with a line fit to the data. Explain how current and voltage are related through a resistor. Give the value of your resistor. //

- Done, see graphs and charts above for Activities 1 & 2.

//Part 2: You should include a graph with a line fit to the data. Explain how current and voltage are related through a bulb; there will be a small difference here relative to the resistor. Give the resistance of the light bulb. Why is it difficult to give a single value for resistance?//

- Line of best fit is included in both graphs. As the bettery voltage is increased, the resistance within the light bulb will also increase. This is shown above in the non-Ohmic Device graph and chart (Activity # 2). One can see from the data that the current and voltage increase more proportionally in comparison to the voltage and resistance. It essentially depends on what the voltage is, but the resistance is not directly proportional to the voltage. To support this, one can see that the resistance does change a bit and it is not linear. This is why it is difficult to give a single value for resistance.

__Light Bulb Activity Information (Class Conversation)__: When a light bulb turns on and off, a significant spike goes upward on the graph projected on the board in class. In addition, there is a significant spike downward when the light bulb is turned off. However, once the light remains on, the graph depicts a very slow increase the seems to taper off. The graph has a spike when the light is turned on because a lot of electrons start to move as soon as the light becomes apparent. Also, the shape of the curve on the graph gets shallower and shallower as Dr. Pasquini turned up the voltage. There is evidently a change in the current as the voltage is increased because this is what lights the bulb. The higher the voltage, the brighter the bulb and the hotter the filament—this causes a decrease in the resistance. When the temperature of the filament changes, so does the resistance. This strays from Ohms law and as a result, this circuit is non-Ohmic.



//Part 3: What patterns do you notice in the currents and voltages for the series circuit? One quantity should be nearly the same for all resistors, one should sum to give something related to the power supply. Use the current and voltage that you measured, give a value for each resistor. Compare these to 100 ohm, 67 ohm, and 460 ohm. Try making this cirart:cuit in the simulation and compare the measurements made with your circuit to measurements in the simulation. Do you see any patterns with the simulation? Include a screenshot in your lab.//

__Series Circuit Chart__: Resistor 1 Resistance (green, copper, brown, back, brown): 0.101 Ohms Resistor 2 Resistance (yellow, purple, redish brown, gold): 0.462 Ohms Resistor 3 Resistance (dark blue, light blue, black, yellow-gold): 0.065 Ohms
 * **Target Voltage** || **Battery Voltage** || **Current in Circuit** || **Resistor 1 Voltage** || **Resistor 2 Voltage** || **Resistor 3 Voltage** ||
 * 4.5 V || 5.02 V || 8.5 Amps || .86 V || 3.93 V || 0.55 V ||
 * 9 V || 9.95 V || 16.2 Amps || 1.64 V || 7.49 V || 1.06 V ||

__Explanation of Patterns__: For the series circuit, there is a current and voltage pattern. The current, or flow of electrons, moving through the circuit remains at a constant pace. We were able to see this through the simulation. This is because it flows out of the battery and has to then flow thrown each of the three resistors in order to get back to the battery again. When elements like resistors are in series, the current has to be the same. It is just the nature of the series circuit. The voltage across the resistors is different; however there is still a pattern. When the Target Voltage was doubled to 9 V (refer to series circuit chart), the resistor values were also doubled. If one adds the voltage of each resistor together, they can get the Battery Voltage. For example, when the Target Voltage is at 4.5 V and the Battery Voltage is at 5.02 V, Resistor Voltage 1's value plus Resistor Voltage 2's value plus Resistor Voltage 3's value equals 4.8 V (0.86 V + 3.93 V + 0.55 V = 4.8 V). This is ultimately the same as the battery voltage. Same goes for the 9 V as the Target Voltage and 9.95 V as the Battery Voltage; Resistor 1 (1.64 V) + Resistor 2 (7.49 V) + Resistor 3 (1.06 V) = 10.19 V. In addition, Ohms Law can apply here:

V = I * R 0.07 Amps * 6.7 Ohms = 0.48 V 0.07 Amps * 10 Ohms = 0.7 V 0.07 Amps * 46 Ohms = 3.3 V

__Diagrams__:



//Part 4: What patterns do you notice in the currents and voltages for the parallel circuit? One quantity should be nearly the same for all resistors; one should sum to give something related to the power supply. Using the current and voltage that you measured, give a value for each resistor. Compare these to 100 ohm, 67 ohm, and 460 ohm. Try making this circuit in the simulation and compare the measurements made with your circuit to measurements in the simulation. Do you see any patterns with the simulation? Include a screenshot in your lab.//

__Parallel Circuit Chart__: Resistor 1 Resistance (green, copper, brown, back, brown): 0.12 Ohms Resistor 2 Resistance (yellow, purple, redish brown, gold): 0.473 Ohms Resistor 3 Resistance (dark blue, light blue, black, yellow-gold): 0.067 Ohms
 * **Target Voltage** || **Battery** **Voltage** || **Current in Circuit** || **Resistor 1 Voltage** || **Resistor 2 Voltage** || **Resistor 3 Voltage** ||
 * 4.5 V || 4.49 V || 123.3 Amps || 40.2 V || 9.5 V || 59.4 V ||
 * 2.5 V || 2.71 V || 74.5 Amps || 24.3 V || 5.7 V || 35.8 V ||

__Explanation of Patterns__: For the parallel circuit, there is a current and voltage pattern. In parallel, voltages don't add to give the battery voltage. Instead, the voltages are all the same. In contrast, the current is not uniform throughout. The currents add together to give the Battery Current and they also split into parts when they reach different junctions in the circuit. Thus, they split and divide among the resistors. One current goes one way and the other current goes in the other direction. The current coming out of the battery knows exactly how to divide because it does the division via Ohms Law:

I = V / R 4.5 V / 46 Ohms = 1 Amp 4.5 V / 10 Ohms = 0.45 Amps 4.5 V / 10 Ohms = 0.67 Amps

__Diagrams__:



//Part 5: Do you see the same patterns you’ve found in parts 3 & 4 in the more complicated circuit? Try making this circuit in the simulation and compare the measurements made with your circuit to measurements in the simulation. Do you see any patterns with the simulation? Include a screenshot in your lab?//

__Series-Parallel Circuit Chart__: Resistor 1: brown, black, brown Resistor 2: yellow, violet, brown Resistor 3: blue, grey, black Resistor 4: brown, black, brown
 * **Resistor 1 Voltage** || **Resistor 1 Current** || **Resistor 2 Voltage** || **Resistor 2 Current** || **Resistor 3 Voltage** || **Resistor 3 Current** || **Resistor 4 Voltage** || **Resistor 4 Current** ||
 * 1.95 V || 19 V || 1.15 V || 2.3 V || 1.12 V || 16.9 V || 1.98 V || 19.1 V ||

__Explanation__: As soon as the electrons from the battery flow through the first resistor in series, the current changes. From the simulation, it appears that their speed divides in two and the electrons also divide and one goes down the path of one junction and the next goes down the other. Once the electrons pass through the resistors that are in parallel, the two junctions meet and then the pass through the next resistor in series. The electrons go from being in two junctions to one and as they pass through the resistor in series, they speed up again and then return to the battery. Essentially, this is combining my explanation for the series circuit and the parallel circuit. Also, Ohms Law is evident here too.

__Diagrams__:



//**Conclusion**: Conclusion: What is meant by the terms current and voltage? How do current and voltage behave in circuits, particularly series circuits and parallel circuits? What is meant by resistance? How does resistance relate current and voltage? What differences exist between simulated circuits and your real circuits? //

Currents flow or pass from one thing to another in an onward motion. In this case, currents flow if a circuit is complete. Voltage is essentially a push or force of electricity. To be more precise, it represents the electric potential energy per unit charge and is a measurement of energy within an electric field. Current is measured in Amps and voltage is measured in volts. They both play significant roles in circuits. As one increases the current, the voltage increases as well. For a series circuit, the current remains the same as it pass through the resistors. However, the voltage is in fact different. Also, when the voltages are added together, the will add up to make the battery voltage. For a parallel circuit, the voltages do not add to give the battery voltage. Instead, they are all the same. Also, the currents are not the same. They divide and add together to give the battery voltage. These circuits both express Ohms Law. The resistance of an object is a measurement of its opposition to steady movements of electrons within a circuit. Resistance is related to voltage and current via Ohms Law. Ohms Law states that the current that flows through a conductor between two points is proportional to the voltage across those same two points. In addition, it is inversely proportional to the resistance between the points. The difference between the simulated circuits and the real circuits is that the simulated circuits are much more accurate in viewing and understanding data. While the real circuits are still very beneficial, they do have some slight inaccuracies.

I do feel that this experiment does produce a very valid and reproducible result. The data that we collected with the real circuits was close to that of the imulation results and patterns that we found. I think that using the simulation helped us to view these results more accurately but the results produced were very alike and with using the real circuits, we were able to still see the same patterns. The equipment was simply a little innacurate or hard to be precise.