% Electrical bridge, electr2.m
clear                       % variables
format short e              % E format
volt1 = 100
volt5 = 0

k12 = 1/2;  k23 = 1/5
k34 = 1/10; k24 = 1/5
k35 = 1/4;  k45 = 1/3
k22 = k12 + k23 + k24
k33 = k23 + k34 + k35
k44 = k24 + k34 + k45
k55 = k35 + k45
beta = k12*1e7              % zienk factor

stiff = [ k12   -k12    0      0    0   % stiffness 
         -k12    k22  -k23   -k24   0
          0     -k23   k33   -k34 -k35
          0     -k24  -k34    k44 -k45
          0      0    -k35   -k45  k55 ];
df =   [ volt1*beta;  0; 0;  0; volt5*beta ] % combined 
zienk = stiff;
zienk(1,1)=zienk(1,1)+beta;
zienk(5,5)=zienk(5,5)+beta

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

% print the results
fprintf('\n   Electr2 Bridge ')
fprintf('\n  Your name, ES 421, ')
disp(date)

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

%  Electr2 Bridge
% Your name, ES 421, 01-Apr-2004

%    Node    Volts    Current
%      1    100.00     16.05
%      2     67.89     -0.00
%      3     29.43      0.00
%      4     26.09     -0.00
%      5      0.00    -16.05