Department of Physics, Engineering Physics and Astronomy: ENPH 353 Engineering Physics Lab II Collection

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    Quantized Conductance – A Study of Atomic Scale Conductance in Gold, Copper, Platinum, and a Platinum-Rhodium Alloy
    (2023-02-23) Hamilton, Claire; McHaffie, Scott; Ripstein, Ethan; Lam, Katrina; Morrison, Nicholas
    Quantized conductance is the study of electron flow at the atomic level. One can observe quantized steps when a wire is stretched to its breaking point. At this point, the two sides of the wire are held together only by a nanometer wide chain of atoms, allowing small amounts of electrons to flow. As the wire breaks and reforms, voltage steps can be measured and displayed on an oscilloscope. The inclusion of a piezo-electric actuator allows one to observe multiple break events per second. The experiment was conducted for 4 different metals: gold, copper, platinum, and a platinum-rhodium alloy. All samples were tested in air and in a nitrogen gas saturated environment, at room temperature. The results suggested quantized conductance of copper in the nitrogen saturated environment with peaks on the conductance histograms located at 1.554 ± 3.647E-3 and 2.032 ± 3.319E-3. The peak locations indicate multiples of the quantum of conductance. Gold was found to have peaks at 0.7720 ± 1.530E-4 and 2.722 ± 2.276E-2 in a nitrogen-rich environment, and 0.7775 ± 2.344E-2 and 1.013 ± 5.274E-1 in an open system. The platinum was analyzed to have a peak at 1.045 ± 1.662E-3 in a nitrogen-rich environment, but none were observed in an open system. The platinum rhodium sample had a peak at 1.250 ± 4.241E-6 in a nitrogen saturated environment and 2.355 ± 1.563E-4 in an open system. In general, histograms produced from the gathered data yielded 0 to 2 quantization peaks but were not centered at predicted values. This discrepancy is likely due to the lack of noise mitigation in the setup.
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    Effect of Changing Electrode Spacing and axial Magnetic Field on Patterns Striations in Low Pressure Gas
    (2023-02-22) Behro, Ewan; Carlyle, Seamus; Katrusiak, Alex; Palos, Brandon; Yeaman, Thomas
    The purpose of this experiment is to see how different input parameters affect plasma striations created by a high voltage across a low-pressure gas. These parameters include the electrode spacing, gas pressure, gas type, and axial magnetic field along the tube. By varying these parameters and comparing them with existing models and prior observations, a greater understanding of plasma is gained. Key findings from this experiment include that the striations remain at the same spacing when held at constant pressure. Another key finding was that the positive column changes length changes linearly with electrode spacing. As a function of electrode spacing, the slope was 1.00±0.03 and intercept −2.1±0.5cm in air and a slope of 0.83±0.04 and intercept −3.4±0.8cm for argon. The breakdown voltage of both argon and air as a function of the product of electrode spacing and gas pressure follow what is known as a Paschen curve of the form [equation] with the constants for argon being A = 12.04 (cm Torr)-1, B = 157.44 (cm Torr)-1, 𝛾𝛾= 0.011. A fit for air could not be obtained. Lastly, it was observed that applying a magnetic field on the plasma with a Helmholtz coil contracted the positive column length. These results are significant because the breakdown voltage of gases can be predicted based on the input parameters of the system and by applying magnetic fields to plasma, the shape can be influenced. The experiment concluded that Paschen’s law can be verified through experimental methods. More experiments should be done to further understand how plasma reacts to a magnetic field.
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    Predicting Straight-Edge Diffraction using a Neural Network
    (2023-02-22) Goldberg, Graham; Bekheet, Ali; Zagar, Mike
    In this experiment we studied the physical effect of diffraction through a straight edge and used a neural network to model and predict the behavior given its parameters. Straight edge diffraction studies how light will interfere with itself when directed towards a straight opaque edge. We used the apparatus to generate a set of data to train on a neural network to predict the diffraction pattern. By using Fresnel’s mathematical model of predicting a diffraction pattern, we trained the neural network with the noiseless theoretical data. The neural network was then able to predict the sliced diffraction pattern to an accuracy of 99.5%.
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    Determining the Curie Temperature of Nickel and Kanthal A-1 with Resistive Heating
    (2023-02-21) McKee, Izzy; Neale, Will; Poltoranos, Andrew; Hogarth, Georgia
    In this experiment Nickel and Kanthal-A wire were heated through resistive heating to find their respective Curie temperatures. High electrical current passed through the wires to heating them to temperature where the materials lost their ferromagnetic properties, becoming paramagnets, shown physically by disconnecting from a permanent disc magnet. The Nickel wire was found to have a Curie temperature of 343.33 °C and it reached this in 40 seconds when the voltage source was set to 10 V. Kanthal-A was unable to be heated to the expected Curie temperature due to the physical power limitations of the circuit. The experimental Curie temperature for Nickel did agree with the theoretical temperature of 350 °C and any discrepancies are attributed to the manual method of current increase.
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    Phase Shift and The Jumping Ring
    (2023-02-08) Luke, Ella; Bronkhorst-Ilavsky, Simon; Rantz, Lucas; Littmann, Nika
    This experiment centered around and developed the model of the Thomson Jumping Ring. The purpose of this experiment was to move past the weak Lenz’s Law justification and provide another explanation for the jumping phenomena: the phase shift between driving and induced currents. By measuring the driving and induced currents for a range of frequencies, the phase shift was determined. The phase shift was compared to induced current and it was shown that induced current is directly proportional to sin of the phase shift, demonstrating that induced current increases at higher phase shifts. Larger induced currents lead to stronger force interactions with the solenoid’s magnetic field, which shows that the magnitude of the force acting on the ring is related to phase shift. The jump height of the ring and observations of its behaviour when it was allowed to levitate proved that the direction of the force acting on the ring is also importantly proportional to phase shift. At small phase shifts, the force acting on the ring oscillates between pushing it up and pulling it down, and as phase shift increases the force proportionately spends more time per oscillation pushing up. At very high frequencies, the force acts entirely to push the ring upwards. These two dependencies on phase shift, one for the magnitude of force and one for direction of the force, show that Lenz’s Law is not enough to describe the Thompson Jumping Ring phenomena, and that an analysis of the ring and solenoid current phase shift is required.