PSPICE Webassign Homework

The latest Webassign homework assignment was designed as further practice in utlilizing PSPICE to solve circuit problems. The two problems were worked out by hand first and the answers were then compared to PSPICE analysis results. The first problem was as follows;

In order to solve the problem. The circuit was first constructed in PSPICE schematic with the exception of the Load being replaced with a probing current source. The idea is to run a sweep across the load with various currents (0-1 mA) with 0.1 mA increments. The results were then plotted. Here is a screenshot;

In this case, the 0-intercept (where the resistance across the load is infinite which is why the current is 0) is the Thevinin voltage while the slope of the line (voltage/current or V/I) is the Thevinin Resistance. The second problem also incorporated calculations for the maximum power displacement across the resistor. The question is as follows.

The first part of the problem was solved in the same method described for problem one. The second part of the problem involved using an actual sweeping resistance across the Resistor. The following screenshot shows the graph along with the circuit constructed in PSPICE Schematic.

With various theoretical resistances across the load, the resulting power dissipation graph was plotted so as to determine the optimum power dissipation.

Overall the results were very close to the calculated values (well within 5% which can be attributed to rounding errors). PSPICE demonstrates that there is a way with the computational power of a PC to calculate values across a circuit by setting a varying source or load and then plotting the results. The graph can then be analyzed and used to find the appropriate values. However, the PSPICE graph also gives the engineer and idea of how the circuit would operate across multiple conditions and save the engineer a lot of tedious calculations and time!