Coulomb's Law

%% Coulombs Law for TWO POINT charges
%{
This program is able to calculate the force, distance, or an unknown charge
when given the other variables. Allows users to calculate solutions by
inputting manual charge quantities or by using elementary charges i.e.
protons and electrons. Comments and clarifications are available at the end
of the script. New edits are: force and distance can now be calculated with
two proton groups or two electron groups, warning messages pop up for distance
calculations if there is only one negative value input.
%}
%% Code start
clc,clear

ElecCharge = -1.6022*10^-19;          %[C] Charge on an electron
ProCharge = 1.6022*10^-19;            %[C] Charge on a proton
k = 9*10^9;                           %[N*m^2/C^2] Coulomb's law constant

% Start of the selection statements

    % Does the equation require the use the a number of protons and
    %   electrons or are the values of the charges altogether different?
c = input('Does the equation call for protons and electrons or different charges?\n');
switch c
    case 1 % Protons and electrons
        % Does the force between a number of protons and electrons need to
        %   be calculated?
        b = input('Calculate the force, the distance, or unknown charge?\n');
            switch b

                % The force is the unknown value and needs to be calculated.
                case 1 % force
                    disp('Okay beginning to calculate the force of elementary charge(s)');

                    % Does the problem require you to use protons, electrons,
                    %   or both elementary charges? The number of elementary
                    %   charges will asked later. This question only needs to
                    %   know which elementary charge(s) is/are involved.
                    e = input('\nDoes the problem deal with protons, electrons, or both?\n');
                    switch e

                        case 1 % Protons only

                            % Is there another charge that needs to be
                            %   input or does the other charge contain
                            %   protons as well. The second option would be
                            %   used in a situation where two nuceli have a force on each other.

                            w = input('Do protons contribute to one or both of the point charges?\n');
                            if w == 1 % Protons are in 1 object

                                % How many protons can now be entered
                                %   below.
                                f = input('How many protons are there?\n');
                                TotalPCharge = f * ProCharge;         % [C] The total amount of charge in the protons.
                                OtherCharge = input('What is the charge of the other object in Coulombs?\n');
                                d = input('What is the distance between the two point charges in meters?\n');
                                d2 = d^2;
                                F = (k*TotalPCharge*OtherCharge)/d2;
                                fprintf('The force is %e N\n', F)
                            elseif w == 2 % Protons are in 2 objects

                                % Do both charges have the same amount of
                                %   protons, i.e. do they have the same
                                %   magnitude
                                y = input('Are these charges the same');
                                    if y == 0 % Indentical groups

                                        % Two similar groups of protons are
                                        %   be used in this calculation
                                        z = input('How many protons are there in each group?\n');
                                        TotalPCharge = z * ProCharge;         % [C] The total amount of charge in the protons.
                                        d = input('What is the distance between the two point charges in meters?\n');
                                        d2 = d^2;
                                        F = (k*TotalPCharge^2)/d2;
                                        fprintf('The force is %e N\n', F)
                                    elseif y ==1 % Different groups
                                        aa = input('How many protons are there in the first object?\n');
                                        TotalPCharge1 = aa * ProCharge;         % [C] The total amount of charge in the protons.
                                        ab = input('How many protons are there in the second object?\n');
                                        TotalPCharge2 = ab * ProCharge;
                                        d = input('What is the distance between the two point charges in meters?\n');
                                        d2 = d^2;
                                        F = (k*TotalPCharge1*TotalPCharge2)/d2;
                                        fprintf('The force is %e N\n', F)
                                    end
                            end
                        case 2 % Electrons only

                            % Is there only one point charge with electrons
                            %   or two? The latter option may not be used
                            %   very often.
                            ac = input('Do electrons contribute to one of both of the point charges?\n');
                            if ac == 1

                                % There is another point charge besides the
                                %   group of electrons that needs to be
                                %   accounted for.
                                h = input('How many electrons\n');
                                TotalECharge = h * ElecCharge;       % [C] The total charge from the electrons
                                Othercharge = input('What is the charge of the other object in coulombs\n');
                                d = input('What is the distance between the two point charges in meters?\n');
                                d2 = d^2;
                                F = (k*TotalECharge*Othercharge)/d2;
                                fprintf('The force is %e N\n',F )

                            % Electrons account for both of the point
                            %   charges
                            elseif ac == 2

                                % Do both of the point charges have the
                                % same number of electrons and magnitude?
                                ad = input('Are the charges the same in magnitude?\n');

                                % Yes there are two indentical point
                                %    charges
                                if ad == 0
                                    ae = input('How many electrons are in each point object?\n');
                                    totalecharge = ae * ElecCharge;
                                    d = input('What is the distance between the point charges in meters?\n');
                                    d2 = d^2;
                                    F = (k*totalecharge^2)/d2;
                                    fprintf('The force is %e N\n',F )

                                % No they are not the same in magnitude and another set
                                %   of electrons must be accounteds for
                                elseif ad == 1
                                    af = input('How many electrons are in the first object?\n');
                                    TotalECharge1 = af * ElecCharge;
                                    ag = input('How many electrons are in the second object?\n');
                                    TotalECharge2 = ag * ElecCharge;
                                    d = input('What is the distance between the point charges in meters?\n');
                                    d2 = d^2;
                                    F = (k*TotalECharge1*TotalECharge2)/d2;
                                    fprintf('The Force is %e N\n',F)
                                end
                            end
                        case 3 % Protons and electrons

                            % How many protons are there
                            p = input('The number of protons\n');
                            totalPCharge = ProCharge * p;
                            l = input('The number of electrons\n');
                            totalECharge = ElecCharge * l;
                            d = input('What is the distance between the two point charges in meters?\n');
                            d2 = d^2;
                            F = (k*totalECharge*totalPCharge)/d2;
                            fprintf('The force is %e N\n',F )
                        otherwise
                            disp('Action could not be completed')
                    end     % switch for force

                % The distance is the unknown value and needs to be
                %   calculated
                case 2 % Distance
                    m = input('Does the problem involve protons, electrons, or both?\n');
                    switch m

                        % The problem only involves protons as the
                        %   elementary charge
                        case 1 % Protons only
                            ah = input('Do protons count for one or two of the point charges?\n');
                            if ah == 1 % Protons are in 1 object
                                n = input('How many protons?\n');
                                TotalpCharge = n * ProCharge;         % [C] The total amount of charge in the protons.
                                otherCharge = input('What is the charge of the other object in Coulombs?\n');
                                Force = input('What is the force between the point charges in Newtons');
                                d2 = (k*TotalpCharge*otherCharge)/Force;
                                d = sqrt(d2);
                                fprintf('The distance between the point charges is %e m\n', d)
                            elseif ah == 2 % Protons are in 2 objects

                                % Do both of the point charges have the
                                %   same number of electrons and magnitude?
                                ai = input('Are the charges the same in magnitude?\n');

                                % Yes there are two indentical point
                                %    charges
                                if ai == 0
                                    aj = input('How many protons are in each point object?\n');
                                    totalPcharge = aj * ProCharge;
                                    Force = input('What is the force between the point charges in Newtons');
                                    d2 = (k*TotalpCharge^2)/Force;
                                    d = sqrt(d2);
                                    fprintf('The distance between the point charges is %e m\n',Force )

                                % No they are not the same in magnitude and another set
                                %   of protons must be accounted for
                                elseif ai == 1
                                    ak = input('How many protons are in the first object?\n');
                                    TotalPCharge1 = ak * ProCharge;
                                    al = input('How many protrons are in the second object?\n');
                                    TotalPCharge2 = al * ProCharge;
                                    Force = input('What is the force between the point charges in Newtons');
                                    d2 = (k*TotalpCharge1* TotalPCharge2)/Force;
                                    d = sqrt(d2);
                                    fprintf('The distance between the point charges is %e m\n',Force )
                                end
                            end

                        % The problem only involves electrons as the
                        %   elementary charge.
                        case 2 % Electrons only
                            am = input('Do electrons count for one or two of the charges?\n');
                            if am == 1
                                o = input('How many electrons?\n');
                                TotaleCharge = o * ElecCharge;         % [C] The total amount of charge in the protons.
                                    if TotaleCharge < 0
                                        disp('You have entered a negative charge. Make sure either the force or other charge is negative or the answer will not be accurate')
                                    end
                                othercharge = input('What is the charge of the other object in Coulombs?\n');
                                force = input('What is the force between the point charges in Newtons\n');
                                d2 = (k*TotaleCharge*othercharge)/force;
                                d = sqrt(d2);
                                fprintf('The distance between the point charges is %e m\n', d)
                             elseif am == 2
                                an = input('Do both charges have the same amount of electrons?\n');
                                    if an == 0
                                        ao = input('How many electrons are in each point oject?\n');
                                        totalEcharge = ao * ElecCharge;
                                        Force = input('What is the force between the point charges in Newtons');
                                        d2 = (k*totalEcharge^2)/Force;
                                        d = sqrt(d2);
                                        fprintf('The distance between the point charges is %e m\n', d)
                                    elseif an == 1
                                        ap = input('How many electrons are in the first point object?\n');
                                        TotalECharge1 = ap * ElecCharge;
                                        aq = ipnut('How many electrons are in the second point object?\n');
                                        TotalECharge2 = aq * ElecCharge;
                                        Force = input('What is the force between the point charges in Newtons');
                                        d2 = (k*totalEcharge^2)/Force;
                                        d = sqrt(d2);
                                        fprintf('The distance between the point charges is %e m\n', d);
                                     end
                             end
                        % The problem requires both elementary charges
                        case 3 % Protons and electrons
                             r = input('Number of protons?\n');
                             totalpCharge = r * ProCharge;
                             s = input('Number of electrons?\n');
                             totaleCharge = s * ElecCharge;
                                if totaleCharge < 0
                                    disp('You have entered a negative charge. Make sure the force negative or the answer will not be accurate')
                                end
                             force = input('What is the force between the point charges in Newtons\n');
                             d2 = (k*TotaleCharge*othercharge)/force;
                             d = sqrt(d2);
                             fprintf('The distance between the point charges is %e m\n', d)
                        otherwise
                            disp('Action could not be completed')
                    end         % switch for distance

                % Either Protons or electrons are being used, BUT there is
                %   an unknown charge that needs to be calculated
                case 3 % missing charge

                    % Determining whether the known charge is from protons
                    %   or electrons
                    t = input('Does the problem use protons or electrons as the given charge?\n');
                    if t == 1

                        % If the charge is from protons
                        u = input('Enter the number of protons\n');
                        KnownCharge = u * ProCharge;
                    elseif t == 2

                        % If the charge is from electrons
                        v = input('Enter the number of electrons\n');
                        KnownCharge = v * ElecCharge;
                    end % If statement
                    F = input('Force in Newtons\n');
                    d = input('Distance between objects in meters\n');
                    d2 = d^2;
                    UnknownCharge = (F*d2)/(k*KnownCharge);
                    fprintf('The unknown charge is %e\n Coulombs', UnknownCharge)
                otherwise
                        disp('Action could not be completed')
            end     % switch
    % No it does not require the use of protons and electrons and requires
    %   manual input of the charge quantities
    case 2 % specific charges

        % Should the end result be the distance between charges, the force
        %    or magnitude of the charges on each other, or do you need to find
        %   a specific charge given everything else?
        a = input('Calculating distance, force, or missing charge?\n');
        switch a

            % The distance between the two point charges needs to
            %   calculated. The answer will come out in meters.
            case 1      % distance
                F = input('Force in Newtons\n');
                Q1 = input('Charge on object 1 in C\n');
                Q2 = input('Charge on object 2 in C\n');
                if (F < 0) || (Q1 < 0) || (Q2 < 0)
                    disp('One of your values were negative. Checking to see if an error will occur ')
                    if (F<0) && (Q1<0) || (F<0) && (Q2<0) || (Q1<0) && (Q2<0)
                        while (F<0) && (Q1<0) && (Q2<0)
                            disp('An error will occur please reevaluate the input values ')
                            F = input('Force in Newtons\n');
                            Q1 = input('Charge on object 1 in C\n');
                            Q2 = input('Charge on object 2 in C\n');
                        end
                        disp('No error will occur. Calculating.')
                    else
                        disp('An error will occur please reevaluate the input values ')
                            F = input('Force in Newtons\n');
                            Q1 = input('Charge on object 1 in C\n');
                            Q2 = input('Charge on object 2 in C\n');
                    end
                end
                d2 = (k*Q1*Q2)/F;
                d = sqrt(d2);
                fprintf('The distance is %e\n m', d)

            % The force or the magnitude from one charge to another needs
            %    to be calculated. The answer will come out in Newtons.
            case 2      % force
                Q1 = input('Charge on object 1 in Coulombs\n');
                Q2 = input('Charge on object 2 in Coulombs\n');
                d = input('Distance between objects in meters\n');
                d2 = d^2;
                F = (k*Q1*Q2)/d2;
                fprintf('The force is equal to %e\n N', F)

            % The charge of another point object needs to be calculated.
            %   The answer will come out in Coulombs.
            case 3      % missing charge
                F = input('Force in Newtons\n');
                Q = input('Known charge on object in Coulombs\n');
                d = input('Distance between objects in meters\n');
                d2 = d^2;
                q = (F*d2)/(k*Q);
                fprintf('The unknown charge is %e\n Coulombs', q)
        end     % switch
end     % if statement

%{
% Comments are made before each selection statement and before some input
%    commands to clarify what is going on in that part of the code. Comments
%    are lined up with specific operations and have a line space between
%    operations.

% It should be noted that for questions with multiple options (e.g. a,b,c)
%    the corresponding number should be input to choose that option (i.e. 1 is
%    a, b is 2). Questions that are yes or no, should be answered 0 or 1 as
%    true or false.

% Variables from outputs that control the branches are generally
%   insignificant and thus have no important name. Variables that are
%   meaningful, like the ones used in the actual equations, have names that
%   represent their values. d and d2 are specific variables whose value
%   changes depending on which branch is used, but its name is the same for
%   simplicity reasons.

% Common conversion factors:
%   cm is 10^-2 m
%   mm is 10^-3 m
%   Angstrom is 10^-10 m
%   fermi is 10^-15 m
%   MN is 10^3 N
%   GN is 10^6 N
%   nC is 10^-9 C
%}