wwallaceLab2

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Apr 3, 2024

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Lab 1 – Ohm’s Law and Diodes Liam Wallace University of Guelph PHYS 1010 Sameer Al-Abdul-Wahid January 14, 2023

Experiment 1 Methods: To start the experiment the IOLab device was connected to the laptop. The breadboard, two 1000 Ω resistors, and three alligator clips were retrieved from the kit. The resistors were placed in series on the breadboard. The alligator clips were connected to the 3.3V, GND, and A7 ports with the other ends being placed on the far side of the left resistor, the far side of the right resistor, and alone respectfully. The alligator clip connected to the A7 port on the IOLab device was used as a probe to find the different amounts of voltage before the first resistor, in between the two resistors, and after the second resistor. This data was recorded to be used within the experiment. The figure to the right shows how the experiment was setup. Results: Potential across resistor (V) Resistance ( Ω ) Current through resistor (mV) Resistor 1 1.647 1000 Resistor 2 1.647 1000 Potential Reading (V) Location 1 3.300 Location 2 1.647 Location 3 0.000

1. The reading that should be expected when touching the probe to the first location is 3.300V which is the voltage that should be coming through the alligator clip into the resistor. This is to be expected as the voltage has not gone through the resistor yet and therefor should not have lost any volts. The voltage reading found in the experiment was 3.300V just as expected. 2. The reading that should be expected when the probe is attached to the ground is 0V. The voltage reading found in the experiment was 0V. 3. Because probe location two is between the two resistors it does not matter where you place the probe. The resistors are in series and there for between them the voltage will stay consistent as long as there are no outside factors. There was no outside factors and the voltage stayed consistent between the two resistors. Conclusion: The theoretical and experimental values of the currents through the resistors were quite similar to one another. This is because the circuit is in series and as the voltage passes through the resistors the current stays the same. Experiment 2/3 Methods: Experiment two started by taking the circuit from experiment one and replacing one of the 1000 Ω resistors with a 1 Ω resistor. The alligator clips were then taken off and replaced by six different alligator clips. Clips 1 and 2 were plugged into the DAC and GND ports and attached to the far side of the 1000 Ω resistor and the far side of the 1 Ω resistor respectfully. Clips 3 and 4 were plugged into the A7 and A8 ports and were attached to the positive side of the 1000 Ω resistor and the negative side of the 1000 Ω resistor. Finally clips 5 and 6 were plugged into the G+ and G- ports and were attached to the positive side of the 1 Ω resistor and the negative side of the 1 Ω resistor. The IOLab software was switched to expert mode and recordings were taken of multiple voltages. The figure to the right shows the experimental setup. Experiment 3 started by adding a red diode between the two resistors on the circuit from experiment 2. An alligator clip was then placed on the negative side of the diode and plugged into port A9. Readings were then taken for multiple voltages before the green diode

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was then used to replace the red one. The same prosses continued with the green diode. The figures below show the experimental setup. Results: 1000 Ω Resistor DAC Output (V) Change in Voltage (V) Current (mV) 0.0 0.0 0.0 0.4 0.413 0.413 0.8 0.863 0.863 1.2 1.121 1.121 1.6 1.539 1.539 2.0 1.980 1.980 2.4 2.355 2.355 2.8 2.650 2.650 3.2 3.012 3.012 Red Diode 0.0 0.0 0.0 0.4 0.410 0.410 0.8 0.843 0.843 1.2 1.160 1.160 1.6 1.541 1.541 2.0 1.636 1.636 2.4 1.678 1.678 2.8 1.689 1.689 3.2 1.710 1.710 Green Diode 0.0 0.0 0.0 0.4 0.426 0.426 0.8 0.835 0.835 1.2 1.180 1.180 1.6 1.585 1.585

2.0 1.768 1.768 2.4 1.814 1.814 2.8 1.837 1.837 3.2 1.860 1.860 The equation used for the table above was (Change in voltage / given resistance). The given resistance was 1000 Ω so the change in voltage being 1000 times bigger than the current is reasonable. The figure to the right is the graph of voltage vs current in experiment 2. This series had a 1000 Ω resistor before a 1 Ω resistor. The voltage of the circuit increased with the voltage of the DAC port, and as seen in the graph the current also increased with the voltage. The figures below are the graphs of voltage vs current in experiment 3. The graph on the right shows the red diode being used to perform the experiment, and the graph on the left shows the green diode being used to perform the experiment. As seen in the graphs the green diode causes the current rise faster than the red diode does causing a steeper incline. As well the green diode can stay at a higher current once the current starts to plane out. When looking at the graphs closely one can see that although the green may be steeper and taller, it is by a very small margin (something like 0.02). This is reflected by the brightness of the diodes, the green diode was brighter and quicker to turn on then the red diode by a very small margin. Conclusion: As shown by experiment 2 and 3 one can see that the green and red diodes do not follow Ohm ’ s law. This can be seen by there graphs rising steeply before flattening out. If they were following Ohm ’ s law they would rise in a linear matter just as the graph showing the 1000 Ω resistor. This is because the diodes do not have a constant resistance value whereas the resistor does.