Problem 8.2 - Source-Free Response of an RL circuit
*
* The circuit for this problem is from textbook Chap. 8, Exercise 29.
* Calculate "by inspection" the time constant of the circuit. To do
* this, reduce the series and parallel combinations of resistances in
* parallel with the inductance until you have only one resistance and
* the inductance. The appropriate ratio of the two values is the
* time constant.
* The .TRAN command final time should be six time constants for the
* PROBE graph display of the source-free response of the circuit.
*
* Obtain a PROBE graph of the inductance current waveform. Add the
* graph of the node voltage V(1). Print a hard copy of the graph.
*
* If you want a printer listing or a printer-plot of the output, the
* .PRINT and/or .PLOT commands should produce 40 output data points.
*
* ===> CHALLENGE PROBLEM! Using the time constant you have calculated,
* write the expression for the source-free response of the inductance
* current. Using the equation for the voltage across the inductance,
* derive the expression for the node voltage V(1). Use PROBE to graph
* the two expressions on the same graph as the circuit response wave-
* forms. If your expressions are correct, the plots will coincide.
*
R1 1 0 3
R12 1 2 2
R2 2 0 4
L1 1 0 ??? IC=??? ; Enter inductance value and t=0 current.
.TRAN ??? 36 ??? ??? UIC ; Enter parameters for the .TRAN command.
; TSTEP should be TFINAL/40 and the maximum
; step size should be about TFINAL/100. The
; UIC statement is required to include the
; initial inductance current in the problem
; solution.
; Add .PRINT or .PLOT commands as desired
; for listed or printer-plot output.
.PROBE
.END