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3. The Description of the Experimental Device
The method essence consists of the comparison of two

electromotive forces between each other (Fig. 3. 1) where  is battery;
Ex is researched battery; AB is slidewire; C is moving contact; G is

zero-galvanometer.
Current I, created by element  , is divided into two ones I and
1
I in point A. The current depends on the resistance of section AC, on
2
the value and direction of EMF  Current I can be reduced to zero
x 2
by corresponding selection of these values.
Applying the first equation of Kirchhoff’s to unit A, we’ll get

I  I  I (3.1)
1 2

Figure 3.1

While doing the second equation of Kirchhoff’s for closed

circuit AC Ex (clockwise path-tracing), we’ll get
I R  C  I R    (3.2)
2 A x 1 AC x
If I  0
2
  I R (3.3)
x 1 AC
Hence, if there is a lack of current in the galvanometer circuit,
the electromotive force Ex is equal to potential difference between

point A and C of a slidewire. Such equation EMF Ex with a potential
difference on the slidewire is called compensation.

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