Trevor's+circuit+lab

=Resistive Circuit Lab= 2/3/2010


 * Participants**: Trevor Wood
 * Purpose**: The purpose of this lab is to help us understand the relationships between current, voltage, and the effects of resistance in three different circuits.
 * Lab Documents**: Include a link to any documentation provided for the lab or any references used in writing the lab report.


 * Brief Description of Experiment**: This experiment is designed to observe the relationship between a voltage and the current in a circuit. To do this I created four circuits; single resistor, three series resistors, three parallel resistors, and a parallel and series resistor. Along with the actual circuit that was made in class, I also used an online simulation at [|Phet.colorado.edu]. When examining the single resistor and single light bulb circuits I collected the battery voltage, resistor voltage, the current, and the resistance. With the three series resistors and the three parallel resitors I collected the current and the voltages of each resistor at two different target battery voltages. With the mixture of series and parallel circuit I had to use a power supply of 9V and collected the current and voltage of each resistor. (Below from left to right: single resistor circuit, single light bulb circuit, three series risistors cicuit, and three parallel resistor circuit)


 * Data**: Table and graph 1: **Ohmic Resistor**: current vs. voltage

As can be seen in the graph the voltage and current have a linear relationship. Ohm's law can be seen in this table, the resistance is found by the voltage divided by the current. Due to this relationship we can conclude that a higher resistor voltage will create a higher current and vice versa. Also a higher voltage and a smaller resistance will created a larger current. The value of my resistor, which is found by dividing 1 by the slope of the graph, is 362.056 ohm's.

Table and graph 2: **Non-Ohmic device** (light bulb): current vs. voltage



The resistance is found using the slope like before, 1 / 0.06561 = 15.242 ohm's.

Table 3: **Three Series Resistors **
 * **Target Voltage** || **Battery Voltage** || **Current in Circuit (mA)** || **Resistor 1 Voltage** || **Resistor 2 Voltage** || **Resistor 3 Voltage** ||
 * **4.5 V** || **4.5 V** || **6.8** || **3.22** || **0.49** || **0.69** ||
 * **9 V** || **9 V** || **138** || **6.45** || **0.99** || **1.4** ||

Resistor 1 resistance (yellow, purple, maroon, gold): .474 ohms Resistor 2 resistance (blue, grey, black, gold): .072 ohms Resostor 3 resistance (brown,black, brown, gold, green): .101 ohms

In the series resistors the current remains the same because it goes through each of the resistors and remains the same. However in the resistors the voltages are different. I found that the voltages of the resistors added together equals the voltage of the battery.

Tables 4: **Three Parallel Resistors **
 * **Target Voltage** || **Battery Voltage** || **Battery Current** || **Resistor 1 Current** || **Resistor 2 Current** || **Resistor 3 Current** ||
 * **4.5 V** || **4.5 V** || **182.7** || **87.2** || **54.8** || **40.7** ||
 * **2.5 V** || **2.5 V** || **123.8** || **59.2** || **37.2** || **27.4** ||

Resistor 1 resistance (yellow, purple, maroon, gold): .052 ohms Resistor 2 resistance (blue, grey, black, gold): .082 ohms Resostor 3 resistance (brown,black, brown, gold, green): .111 ohms

In the parallel resistors circuit the voltages are the same, but the current changes. This is because the electrons have a choice of where to travel before each resistor. I found that the sum of the resistor's currents is equal to the battery current.

Table 5: **Parallel and Series**
 * **Res.1 Voltage** || **Res. 1 Current** || **Res.2 Voltage** || **Res.2 Current** || **Res.3 Voltage** || **Res.3 Current** || **Res.4 Voltage** || **Res.4 Current** ||
 * **3.43** || **33.1** || **2.12** || **4.5** || **2.12** || **28.5** || **3.40** || **33.1** ||

Resistor 1 resistance (Brown, Black, Brown): .104 ohms Resistor 2 resistance (Yellow, pink, brown)): .471 ohms resistor 3 resistance (Blue, Green, Black): .074 ohms resistor 4 resistance (Brown, Black, Brown): .103 ohms

current = voltage / resistance
 * Sample Calculations:**
 * //Ohm's Law Formula// || The current (Amps) is found by dividing the voltage (Volts) by the resistance (Ohms)

Ohm's Law can be rearranged to find the voltage or the resistance: Voltage = current x resistance

resistance = voltage / current || formula || The resistance of a resistor is equal to 1 / slope (of graph current vs. voltage).
 * Resistance/slope

The slope is equal to 1 / resistance. ||
 * 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?//

Current is the rate that charge flows in a circuit and is measured in amps, it can be related to water and the way it flows through a pipe. The force that pushes this current is the voltage, which is measured in volts. Together they both have huge roles in simple circuits, such as series and parallel circuits. In a parallel circuit the voltage is the same, but the currents are different because the electrons have the choice of which resistor to pass through. In a series circuit the same results are not seen. The current remains the same because it has only one path to take through the resistors, but the voltage in the resistors change. Resistance is simply the voltage divided by the current. Ohm's law shows this relationship between resistance, voltage, and current. The major difference that i found while doing the experiment with the simulated circuits and the real circuits was the accuracy of the numbers and data that were found while using the simulation.

I think that this experiment definately produced a valid result because of how we had two sources to gather data from and how the simulation gave us very precise and accurate numbers for data. Like any human experiment there was some error in collecting data and with reading of numbers and measurements. But this error was solved with the helpful simulations that we could check our numbers over with.