% Electric circuit, ElectS01 loops, 6 nodes
clear                       % variables
format short e
volt1 = 8
volt5 = 10
volt6 = 0

k12 = 1/7;  k23 = 1/7;
k25 = 1/7;  k34 = 1/8;
k46 = 1/6;  k13 = 1/11;
k36 = 1/12;
k11 = k12 + k13;
k22 = k12 + k23 + k25;
k33 = k23 + k34 + k36 + k13;
k44 = k34 + k46;
k55 = k25;
k66 = k36 + k46;
beta = k12*1e7

stiff = [ k11   -k12   -k13    0      0     0  % matr
         -k12    k22   -k23    0    -k25    0
         -k13   -k23    k33   -k34    0   -k36
          0       0    -k34    k44    0   -k46
          0     -k25     0     0     k55    0
          0       0    -k36   -k46    0    k66 ];
df =   [ volt1*beta; 0; 0; 0; volt5*beta; volt6*beta ] % comb
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
volts = inv(zienk) * df;       % displacements
current = stiff * volts        % force vector

% print the results
fprintf('\n   Electric 6x6, Spring 2001, ')
fprintf('\n  Your name,  MENG 421, ')
disp(date)

fprintf('\n   Node     Volts    Current\n')
for i = 1:length(df)
  fprintf('    %2.0f   %7.2f   %7.2f \n',i,volts(i),current(i))
end

%   Electric 6x6, Spring 2001, 
%  Your name,  MENG 421, 07-Apr-2004

%   Node     Volts    Current
%     1      8.00      0.37
%     2      7.55      0.00
%     3      4.65      0.00
%     4      1.99      0.00
%     5     10.00      0.35
%     6      0.00     -0.72