it is being difficult plotting the graph for Capacitance vs Distance D..please provide me a suitable solution to plot the graph

%USING THE METHOD OF MOMENT,

% THIS PROGRAM DETERMINES THE CAPACITANCE OF A

% PARALLEL-PLATE CAPACITOR CONSISTING OF TWO CONDUCTING

% PLATES, EACH OF DIMENSION AA x BB, SEPARATED BY A

% DISTANCE D, AND MAINTAINED AT 1 VOLT AND -1 VOLT

% ONE PLATE IS LOCATED ON THE Z = 0 PLANE WHILE THE OTHER

% IS LOCATED ON THE Z=D PLANE

% ALL DIMENSIONS ARE IN S.I. UNITS

% N IS THE NUMBER IS SUBSECTIONS INTO WHICH EACH PLATE IS

%DIVIDED

% FIRST, SPECIFY THE PARAMETERS

ER = 1.0;

EO = 8.8541e-12;

AA = 1.0;

BB = 1.0;

D = 1.0;

N = 9;

NT = 2*N;

M = sqrt(N);

DX = AA/M;

DY = BB/M;

DL = DX;

% SECOND, CALCULATE THE ELEMENTS OF THE COEFFICIENT

% MATRIX A

K = 0;

for Kl=1:2

for K2=1:M

for K3=1:M

K = K + 1;

X(K) = DX*(K2 - 0.5);

Y(K) = DY*(K3 - 0.5);

end

end

end

for K1=1:N

Z(K1) = 0.0;

Z(K1+N) = D;

end

for I=1:NT

for J=1:NT

if(I==J)

A(I,J) = DL*0.8814/(pi*EO);

else

R = sqrt( (X(I)-X(J))^2 + ( Y(I)-Y(J) )^2 + ( Z(I)-Z(J) )^2 ) ;

A(I,J) = DL^2/(4.*pi*EO*R);

end

end

end

% NOW DETERMINE THE MATRIX OF CONSTANT VECTOR B

for K=1:N

B(K) = 1.0;

B(K+N) = -1.0;

end

% INVERT A AND CALCULATE RHO CONSISTING

% THE UNKNOWN ELEMENTS

% ALSO CALCULATE THE TOTAL CHARGE Q AND CAPACITANCE C

F = inv(A);

RHO = F* (B');

SUM = 0.0;

for I=1:N

SUM = SUM + RHO(I);

end

Q = SUM*(DL^2) ;

VO = 2.0;

C = abs(Q)/VO;

Please provide a suitable solution to plot the graph Capacitance vs Distance

[Shivaputra Narke]

Is this code working as expected?

[ASUTOSH]

yes..just have a problem how to plot the graph Capacitance vs Distance..could you help me on this ??

[Mischa Kim]

As far as I can tell both distance and capacitance are scalars, not vectors. Am I correct? If so, what do you want plot exactly?

[ASUTOSH]

with increase in distance .....i wanted to see how the capacitance changes...because after some point of time there will be fringing effect whoch will cause disruption..so just wanted to check that

[ASUTOSH]

any solutions ?

[ASUTOSH]

please help me with some solutions..if possible

Answer 1

[Youssef Khmou]

you have to measure each time the capacitance with varying d, there is peak at d=0.1, is this reasonable ? :

%USING THE METHOD OF MOMENT,
% THIS PROGRAM DETERMINES THE CAPACITANCE OF A
% PARALLEL-PLATE CAPACITOR CONSISTING OF TWO CONDUCTING
% PLATES, EACH OF DIMENSION AA x BB, SEPARATED BY A
% DISTANCE D, AND MAINTAINED AT 1 VOLT AND -1 VOLT
% ONE PLATE IS LOCATED ON THE Z = 0 PLANE WHILE THE OTHER
% IS LOCATED ON THE Z=D PLANE
% ALL DIMENSIONS ARE IN S.I. UNITS
% N IS THE NUMBER IS SUBSECTIONS INTO WHICH EACH PLATE IS
%DIVIDED
% FIRST, SPECIFY THE PARAMETERS
ER = 1.0;
EO = 8.8541e-12;
AA = 1.0;
BB = 1.0;
N = 9;
NT = 2*N;
M = sqrt(N);
DX = AA/M;
DY = BB/M;
DL = DX;

 D=0:0.001:1;

 for n=1:length(D);
% SECOND, CALCULATE THE ELEMENTS OF THE COEFFICIENT
% MATRIX A
K = 0;
for Kl=1:2
for K2=1:M
for K3=1:M
K = K + 1;
X(K) = DX*(K2 - 0.5);
Y(K) = DY*(K3 - 0.5);
end
end
end
for K1=1:N
Z(K1) = 0.0;
Z(K1+N) = D(n);
end
for I=1:NT
for J=1:NT
if(I==J)
A(I,J) = DL*0.8814/(pi*EO);
else
R = sqrt( (X(I)-X(J))^2 + ( Y(I)-Y(J) )^2 + ( Z(I)-Z(J) )^2 ) ;
A(I,J) = DL^2/(4.*pi*EO*R);
end
end
end
% NOW DETERMINE THE MATRIX OF CONSTANT VECTOR B
for K=1:N
B(K) = 1.0;
B(K+N) = -1.0;
end
% INVERT A AND CALCULATE RHO CONSISTING
% THE UNKNOWN ELEMENTS
% ALSO CALCULATE THE TOTAL CHARGE Q AND CAPACITANCE C
F = inv(A);
RHO = F* (B');
SUM = 0.0;
for I=1:N
SUM = SUM + RHO(I);
end
Q = SUM*(DL^2) ;
VO = 2.0;
C(n) = abs(Q)/VO;
end
figure, plot(D,C);

[ASUTOSH]

?? Error using ==> plot Vectors must be the same lengths.

Error in ==> Capacitance at 70 figure, plot(D,C); this is the error when I try to change the value of d ....??

[ASUTOSH]

means if I am changing the value of d , suppose from D= [0:0.01:5] then the error shows is

?? Error using ==> plot Vectors must be the same lengths.

Error in ==> Capacitance at 70 figure, plot(D,C)

so any solution for this ?

[Youssef Khmou]

ok try the edited code .

[ASUTOSH]

I Am facing anew problem...the problem is i need to change the N (NUMBER IS SUBSECTIONS INTO WHICH EACH PLATE IS DIVIDED) IF am changing the values it is throwing this error :

let i put N=20

?? Attempted to access X(33); index out of bounds because numel(X)=32.

Error in ==> Capacitance at 45 R = sqrt( (X(I)-X(J))^2 + ( Y(I)-Y(J) )^2 + ( Z(I)-Z(J) )^2 ) ;

[ASUTOSH]

any help on this ...because if i change N its showing error as mentioned above..so please help me...

[Patrik Ek]

check the loop

 for Kl=1:2
     for K2=1:M
         for K3=1:M
             K = K + 1;
             X(K) = DX*(K2 - 0.5);
             Y(K) = DY*(K3 - 0.5);
         end
     end
 end

The variables X and Y seems to be dependent on sqrt(N), which will cause trouble with N = 20. It would be more stable to give M a value and define N as

 N = M^2;