We determined that the pulse traveled twice the length of the coaxial cable (approximately 609.6m) in 3.1µs. These figures translate into a value of 1.96645161x108 m/s for its velocity. However, since the pulse is not moving through a vacuum, we needed to make an adjustment to this value in order to find the experimental value of the speed of light. With some knowledge of Maxwell's equations and some vector calculus, we determined an expression that would yield the corresponding value for the speed of light through the polyethelene dielectric (see derivation here). Our results predict the the speed of light to be 2.95622499x108 m/s. This determined value falls within 1.4% error of the accepted value of 2.99792458x108 m/s. Therefore, this experiment represents an accurate method for calculating a value for the speed of light.
Next, we were also able to determine a value for the characteristic impedance of our coaxial cable. We did so by using the graph of the ratio of reflected to input pulse voltages vs. the load resistance across the inner and outer conductors. The graph of this data can be seen again on our experimental page (or just click here). To determine the characteristic impedance of our cable we used Microsoft Excel's SLOPE function to obtain the slope of our data around the points where the x-intercept occurs (the x-intercept being Zo of our cable). Once the slope of the data around the x-intercept was found to be 0.004071 we used the equation y = mx+b to calculate b = -.2167626. Then we used the y=mx+b again setting y = 0 and solving for x which yielded a value of 53.25 Ohms (click here to see full calculations). Our obtained value is within 0.5% error of several manufacturer's determined values.1
Overall, our lab experiment was a success for we were able to determine both the characteristic impedance of the coaxial cable and A value for the speed of light to a great degree of accuracy. Back to the beginning, please.
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1. http://www.ora.com/reference/dictionary/terms/C/Coaxial_Cable.htm