i make this programme in order to get a plot in physics ,, but when i run it ,, i get error which i cant identify and correct it .. please i want a help to identify the correct

syms x;
syms E;
syms A;
syms B;
syms K;
syms T;
syms v;

n=1*10^19;            %number of electrons
area=1*10^-3;         %area
A=2;
w=1*10^-4;           %width 
q=1.6*10^-19;
h=6.6*10^-34;
v=1*10^6;            % electron velocity
K=1.38*10^-23;       %boltzman constant
m=0.5;               %effective mass

Va=0.1:0.1:5        %applied voltage
E=Va/w;
x=(q*Va)/w;

B=A*x.^2;
a=sqrt((E-A)./B);
Twkb=(1./(sqrt(2*m*B*((a.^2)+1./(x^2))))).*exp((2*sqrt(2*m*B/(h^2))).*((-sqrt(a.^2+(1./x^2))./(1/x))+log((1/x)+sqrt(a.^2+(1./x^2)))));

I=area.*q.*v.*n.*Twkb;

semilogy(Va ,I ,'*','r')
xlabel('Applied Voltage (Va)in Volts')
ylabel('current in(A)')

[Geoff Hayes]

Aalaa - please copy and paste the full error message (all the red text) to this question.

[Aalaa Abu alrob]

Error using ^ One argument must be a square matrix and the other must be a scalar. Use POWER (.^) for elementwise power.

Error in current (line 25) Twkb=(1./(sqrt(2.*m.*B.*((a.^2)+1./(x.^2)))))*exp((2*sqrt(2.*m*B/(h.^2)))*((-sqrt(a.^2+(1./x^2))./(1./x))+log((1./x)+sqrt(a.^2+(1./x.^2)))));

Answer 1

[Geoff Hayes]

Aalaa - I suspect the problem is with (at least)

 x^2

x appears to be a 1x50 array and so the error message is telling you that is is invalid for the ^ operation since we can only use ^ if the x is a scalar or a square matrix. Are you trying to square each element of x? If so, then use

 x.^2

instead.

[Aalaa Abu alrob]

yes i try it . but i get other error

Error using * Inner matrix dimensions must agree.

Error in current (line 25) Twkb=(1./(sqrt(2.*m.*B.*((a.^2)+1./(x.^2)))))*exp((2*sqrt(2.*m*B/(h.^2)))*((-sqrt(a.^2+(1./x.^2))./(1./x))+log((1./x)+sqrt(a.^2+(1./x.^2)))))

[Geoff Hayes]

So you will need to look at where you are doing a matrix multiplication operation and ensure that the dimensions of the two matrices are compatible. Start with just

 (1./(sqrt(2.*m.*B.*((a.^2)+1./(x.^2)))))

Does the above line work? It probably should since there is no * for matrix multiplication. So if this does compute and produces a result, then log the dimensions of this matrix. Then do the same for

 exp((2*sqrt(2.*m*B/(h.^2))

Does this work? I think that it might not since this has been coded slightly differently than the first line. Note the

 2.*m*B

vs

 2.*m.*B

Which is correct?

[Aalaa Abu alrob]

i divide it to 3 part (1./(sqrt(2.*m.*B.*((a.^2)+1./(x.^2))))) exp((2*sqrt(2.*m.*B/(h.^2))) ((-sqrt(a.^2+(1./x.^2))./(1./x))+log((1./x)+sqrt(a.^2+(1./x.^2)))) and 3 parts are work ,, and its size are the same[1 50]

[Aalaa Abu alrob]

Thank but has you any comment want to add And can you tell may what i can do to solve it!!

[Geoff Hayes]

well what should the result be? a scalar or a 1x50 array?

[Aalaa Abu alrob]

The result for Twkb must be array in order to substitute in I and get set of data then plot it

[Geoff Hayes]

so how should the three parts of your equation be multiplied together? with .*?

[Aalaa Abu alrob]

Thank I use .* and get result