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//===========================================================================
//chapter 7 example 4
clc;clear all;
//variable declaration
w = 23; //wattmeter reading in watts
Rp = 2000; //resistance in Ω
f = 100; //frequency in Hz
L = 10*10^-3 //inductance
V = 240; //voltage in V
I = 4.5; //current in A
//calculations
Xp = 2*%pi*f*L; //reactance in Ω
theta = atan(Xp/Rp);
theta1 =(theta*180)/(%pi)
//cos(phi)=P/V*I
//phi = acos(P/V*I)
//w = Pt*(cos(theta))*(cos(phi-theta))/cos(phi); //wattmeter reading
W1 = V*I; //V*I in watts
//phi = acos(P/W) = acos(P/1080)
//W = P*cos(theta)*(cos(phi-theta))/cos(phi)
//W =23 =P*cos(0.18)*cos((acos(P/1080))-0.18)/(P/V*I)
//let cos(acos(P/1080)-0.18) =A
//B = cos(0.18)
//W=23 = (P*B*A)/(P/(V*I))
// W= B*A*V*I
//A = W/(B*V*I)
B = cos((theta1*%pi)/180);
A = w/(B*V*I);
//cos(acos(P/1080)-0.18) =A
//C =acos(P/1080) = acos(A)+0.18
A1 =(acos(A))*(180/%pi);
C = A1+0.18
D = cos(C*%pi/180)
P =1080*D;
e = ((w-P)/P)*100; //percentage error in %
//result
mprintf("percentage error in %3.2f percentage ",e);
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