Lab 1 - Resistance

# With respect to temperature t in this section you

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with respect to temperature ( T ). In this section you will explore this difference between an ohmic and non-ohmic resistor and quantify how R depends on T . This will be done by comparing the I vs. V plots (know as an “IV curve”) of a conventional resistor to that of a light bulb. 8.1 Setup The PASCO Power Amplifier will be used to supply the DC voltage. Attach the leads of the Power Amplifier to the two banana plug jacks located on the right side of the Electronics Lab Board (seen in Figure ?? ). Attach two banana plug wires to the two jacks located on the top of the Current Probe. At the other end of the wires attach two gator clips. As discussed earlier in the lab the Current Probe should be connected in series with the circuit element whose current you’re intending to measure. The orientation of the Current Probe with respect to the Power Amplifier is important. Make sure the direction of positive current (as notated on the Current Probe) is consistent with the positive and negative terminals of the Power Amplifier (remember: current flows from high to low potential, i.e. “ + ” - ”) In DataStudio display both the source voltage as well as the current being measured by the Current Probe. 8.2 Approximation of Noise For any experiment it is essential to have a quantitative understanding of the noise in your set- up and how this contributes to the scientific error of your measurements. In the case of this lab you will find there is a random electrical-noise associated with all the elements of your circuit. This manifests itself as random fluctuations in your measurements of voltage. To account for this do the following: Once you’ve set up your circuit but before turning on the signal generator, display the readout of the voltage probe that’s placed across the resistor. This signal should appear essentially flat. Collect a sample of this signal and with this data calculate the average value ( V avg ), which should be approximately V avg = 0. Now calculate the standard deviation of this sweep. Both of these values can be found using the statistics button of the ‘Graph’ display (it looks like: Σ). The standard deviation represents the random noise in your circuit and will be the error in your measurement of voltage across the resistor. 11

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8.3 Data Collection and Plotting Once your equipment is assembled and configured you can now begin to collect data. To do so you simply push the “Start” button at the top left of the main DataStudio screen (as can be seen in Figure ?? and ?? ). If you’re using the default sampling options DataStudio will start a timer and collet data points at the sampling rate specified in the “Signal Generator” window. The data “runs” will be listed at left in the Data List menu, shown in Figure ?? . A set of data is collected for each of the configured probes. To stop collecting data push the “Stop” button; this will finalize the data run. DataStudio can also be configured to allow manual sampling of
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• Spring '11
• shpyrko
• Resistance, Resistor, power amplifier, Current Probe

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