Resistor Connected to a real Battery

%% Resistor Connected to a Real Battery
% Calculates the internal resistance r, the electric current, the power
%   dissipated by the external resistor and battery, and the efficiency of
%   the circuit

% Inputs and Variables
R = input('Resistance of the resistor in Ohms\n');
epsilon = input('What is the electromotive force in Volts?\n');
deltaVt = input('The terminal voltage drop in Volts\n');

% Outputs and Equations
I = deltaVt/R;
r = (epsilon-deltaVt)/I;
PR = R*I^2;
Pr = r*I^2;
Eff = PR/(Pr+PR);
fprintf(['The internal resistance, electric current, power dissipated by \n '...
       'the external and internal resistor, and the efficiency are \n', ...
       '%.4e Ohm,  %.3i A, %.3i W, %.3i W, %.3i \n'], r, I, Pr, PR, Eff)