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+//CHAPTER 8- DIRECT CURRENT MACHINES
+//Example 17
+
+disp("CHAPTER 8");
+disp("EXAMPLE 17");
+
+//VARIABLE INITIALIZATION
+v_t=200;                   //in Volts
+I_l=22;                    //in Amperes
+N1=1000;                   //in rpm
+r_a=0.1;                   //in Ohms
+r_f=100;                   //in Ohms
+N2=800;                    //in rpm
+
+//SOLUTION
+
+//solution (i)
+I_f=v_t/r_f;
+I_a1=I_l-I_f;
+E_a1=v_t-(I_a1*r_a);
+//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a1*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get,
+r_s1=((v_t - ((N2*E_a1)/N1))/I_a1)-r_a;
+disp(sprintf("(i) When the load torque is independent of speed, the additional resistance is %f Ω",r_s1));
+
+//solution (ii)
+I_a2=(N2/N1)*I_a1;
+//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a2*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get,
+r_s2=((v_t - ((N2*E_a1)/N1))/I_a2)-r_a;
+disp(sprintf("(ii)When the load torque is proportional to speed, the additional resistance is %f Ω",r_s2));
+
+//solution (iii)
+I_a2=(N2^2/N1^2)*I_a1; 
+//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a2*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get,
+r_s3=((v_t - ((N2*E_a1)/N1))/I_a2)-r_a;
+disp(sprintf("(iii)When the load torque varies as the square of speed, the additional resistance is %f Ω",r_s3));
+
+//solution (iv)
+I_a2=(N2^3/N1^3)*I_a1;
+//on rearranging the equation E_a2:E_a1=N2:N1, where E_a2=v_t-I_a2*(r_a+r_s) and E_a1=v_t-(I_a1*r_a), we get,
+r_s4=((v_t - ((N2*E_a1)/N1))/I_a2)-r_a;
+disp(sprintf("(iv)When the load torque varies as the cube of speed, the additional resistance is %f Ω",r_s4));
+
+//END
+