An unregulated power supply was tested with three resistors (1 kOhm each) in parallel to the circuit. In this lab, we wanted to maintain 4.75-5.25V (5% variation about 5V) while varying the # of Resistances in parallel. Simplification of calculations was made by adding R's and solving Req, and using the Req and max. and min. of the voltage of the load (Vbus) gave the voltage & resistance of the battery source (Vs and Rs).
Vs = 5.54 V Rs = 54.9 Ohm
Using V=IR, the calculated min. and max. Ibus can be found, which were 5.25mA and 14.25A respectively. For the lab, the power supply had only intervals of 2V, so 6V was used instead of 5V, and a Resistor box measured around 55.4 for the Rs. Measured values of circuits with different # of resisters (loads) were as followed:
Config Req (Ohm) Vbus (V) Ibus (mA) Pload (W)
1 Load 1000 5.72 5.81 -min 0.033
2 Load 500 5.43 10.97 0.060
3 Load 333 5.18 15.6 -max 0.081
All Vbus were within the 5% variation except for the 5.72V (circuit with 1 load). Naturally, the use of 6V would increase all the values of Vbus. The higher Vs (6V, not 5V) also explains the higher min. and max. Ibus, as more current flows as Vs increases and R stays constant. This lab demonstrates that with less Req, there is more current to flow, and using P=VI, shows that more power is applied to the load as well.
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