Phys431-overview

# Phys431-overview - Physics 431 Experiments The Oscilloscope...

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Physics 431 Experiments The Oscilloscope Exercise. This exercise presents the students with the opportunity to learn about the features and capabilities of this most fundamental of laboratory instruments. Students measure signals over a wide range of frequencies and magnitudes to gain a sense of the signal and parameter envelopes within which the oscilloscope is a useful measuring device. The importance of proper triggering is emphasized, and students observe how neglecting this part of the set-up process may completely prevent them from observing the signal of interest. This exercise will involve the use of both analog and digital instruments. Electron Charge Determination from Johnson Noise and Shot Noise Measurements. Students are introduced to the concept that noise is an intrinsic and fundamental characteristic of electronic components and circuits. As such it can be turned from the traditional bane of the experimentalist into a useful tool. The Johnson noise across a resistor is amplified and measured at both room temperature and liquid nitrogen temperature for a series of different resistances. From these measurements students are able to subtract out the amplifier contribution to the measured noise and then determine the dependence of the Johnson noise voltage on the value of the resistance. For the shot noise measurements a series of different currents are passed through a vacuum diode and the shot noise across the diode is measured at each current. Since the current is carried by electron-size charges, the shot noise measurements contain information about the magnitude of the elementary charge " e ". By combining the results of both the Johnson noise and shot noise measurements, students are able to derive a value for the magnitude of this quantity. Hall Effect in Conductors and Semiconductors. In this experiment, students learn about the classical Hall effect which is the basis of most sensors used in magnetic field measurements. Thin film samples consisting of a semiconductor (InAs) and two different metals (aluminum and gold) are investigated to

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Phys431-overview - Physics 431 Experiments The Oscilloscope...

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