First implementation of Modified Nodal Analysis

This is the initial implementation of Modified Nodal Analysis method for solving circuits in Laplace Domain and a first step towards the creation of symbolic circuit solver in Sympy.


> from sympy.circuit import Circuit, solve
> my_cir = Circuit()
> my_cir.add_vsource('V1', '1', '0', '10')
> my_cir.add_inductor('L1', '1', '2', '0.1')
> my_cir.add_capacitor('C1', '2', '3', '0.0001')
> my_cir.add_resistor('R1', '3', '0', '1000')
> solve(my_cir)
> my_cir.G

[ L1*s,           -L1*s,               0]
[-L1*s, L1*s + 1/(C1*s),       -1/(C1*s)]
[    0,       -1/(C1*s), 1/R1 + 1/(C1*s)]
> my_cir.x

[                                        V1]
[L1*V1*s*(C1*s + R1)/(L1*s*(C1*s + R1) + 1)]
[         L1*R1*V1*s/(L1*s*(C1*s + R1) + 1)]
[           L1*V1*s/(-L1*s*(C1*s + R1) - 1)]