In this lab, we created a simple DC circuit with a battery, AWG #30 cables. and a load resistor. The cables themselves were modeled as resistors is series with the load. Besides creating a simple circuit, we wanted to get comfortable using the lab equipment since this was our first lab assignment. One of our purposes was to determine the maximum amount of resistance that the cable could carry while the load could still operate normally. We also wanted to determine the largest distance of cable that could be used which separated the battery from the load. Additionally, we wanted compute the efficiency and to estimate how long it would take to discharge the battery. Our first step was rather straightforward in that we theoretically modeled the active and passive elements of the circuit and computed the fixed load resistance as 1kΩ. Next we gathered the materials needed to conduct the experiment. Since we knew that the load would require a minimum potential of 11V we had to vary the resistance of the cables. By doing so, this would help us determine the maximum amount of resistance the cable could have while the load could still operate properly. We would then keep track of the current through and the voltage across the load by using an ammeter is series and a voltmeter in parallel. respectively. Then we were instructed to measure the components used for the actual experiment using a multimeter. We used a resistor box rated at 1W and a power supply rated with a maximum voltage and current rated at 12 V and 2A, respectively. Using the color code for the load resistor it's nominal resistance was found to be 1kΩ±10Ω. Using the DMM, we found the actual resistance to be 0.977kΩ. We also jotted down the rated power of the resistor which was 1/8 W. We also found it to be within the required tolerance. Our next step was to set up the power supply as close to 12 V as possible by adjusting the knob. We recorded this value to be 12.33 V. Finally came the point where we performed the actual experiment. Noting that the initial variable resistance was to be zero, we were instructed to increase the resistance of the resistance box by increments of 10 Ω until we achieved the minimum load voltage of 11V. Once getting to this point, we recorded the voltage across the load to be 11.0 V, the current supplied from the battery to be 11.3 mA, and the final maximum resistance of the cable to be 105 Ω. The experiment was now completed and we were instructed to disassemble the components. We then got to the process of making data calculations. Considering that the power supply was rated as 0.8 A-hr, we determined time of discharge to be 70.8 hr. The next step was to compute the distribution efficiency. We did so by first computing the power to the load and cable to be 0.121 W and 13.4 mW, respectively. Given these values we noted that they did not exceed the power capability of the resistor box, which we noted earlier was rated at 1W. Then substituting these values into the efficiency equation, we determined the efficiency to be 90.0%. Finally, we were asked to determine the maximum length between the battery and the load, using the total resistance of the cable as a guide. We calculated this to be 304 m. We considered our lab to be a success, especially when you consider our relatively high efficiency of 90.0%. And we also met our other goals mentioned at the beginning of this post as well. Our first laboratory assignment was very enlightening, and hopefully it translates to success in our future lab assignments. The following are some photos that were taking during this lab assignment.
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