% Electric circuit, 3 loops, 6 nodes, electr3.m
clear                       % variables
format short e
volt1 = 20
volt5 = 5
volt6 = 0

k12 = 1/2; k23 = 1/3;
k24 = 1/7; k34 = 1;
k45 = 1;   k36 = 1/8;
k22 = k12 + k23 + k24;
k33 = k23 + k34 + k36;
k44 = k24 + k34 + k45;
k55 = k45;
k66 = k36;
beta = k12*1e7

stiff = [ k12   -k12     0     0      0     0  % cond matrix
         -k12    k22   -k23   -k24    0     0
          0     -k23    k33   -k34    0   -k36
          0     -k24   -k34    k44  -k45    0
          0       0      0    -k45   k55    0
          0       0    -k36     0     0    k66 ];
df =   [ volt1*beta; 0; 0; 0; volt5*beta; volt6*beta ] % d, F
zienk = stiff;
zienk(1,1)=zienk(1,1)+beta;
zienk(5,5)=zienk(5,5)+beta;
zienk(6,6)=zienk(6,6)+beta

format short
displ = inv(zienk) * df;     % displacements
volts = displ'
current = (stiff * displ)'   % force vector

% print the results
fprintf('\n   Electr3 6x6 ')
fprintf('\n  Your name,  MENG 421, ')
disp(date)

fprintf('\n   Node     Volts     Current\n')
for i = 1:length(df)
  disp(sprintf('    %2.0f   %8.2f   %8.2f',i,volts(i),current(i)))
end

%   Electr3 6x6 
%  Your name, ES 421, 11-Apr-2004
  
%  Node     Volts     Current
%    1      20.00       3.00
%    2      14.00       0.00
%    3       8.00       0.00
%    4       7.00       0.00
%    5       5.00      -2.00
%    6       0.00      -1.00