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//===========================================================================
//chapter 10 example 14
clc;
clear all;
//variable declaration
P = 500; //resistance in arm AB in Ω
Q = 500; //resistance in arm BC in Ω
S = 500; //resistance in arm CD in Ω
R = 500; //resistance in arm BD in Ω
Rg = 100; //galvanometer in Ω
E = 10; //battery voltage in V
Rth = 500; //thevenin's equivalent resistanceof bridge Ω
Ig = 10^-9; //galavanometer capable of detecting Ig current in A
//calculations
//Eth = (E*dR)/(4*R);
x = E/(4*R); //thevenin or open -circuit voltage in dR
//Ig = Eth/(Rth+Rg)
y = x/(Rth+Rg); //current through galvanometer
dR = (Ig*(Rth+Rg))/x; //the smallest change in resistance that can be detected in Ω
//result
mprintf("the smallest change in resistance that can be detected = %3.2f m Ω",(dR*10^3));
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