Explanation, Formulas, Solved Example Problems | Kirchhoff’s rule and Wheatstone’s bridge - Comparison of emf of two cells with a potentiometer | 12th Physics : Current Electricity
Chapter: 12th Physics : Current Electricity
Comparison of emf of two cells with a potentiometer
Comparison of emf of two cells with a
potentiometer
To compare the emf of
two cells, the circuit connections are made as shown in Figure 2.28.
Potentiometer wire CD is connected to a battery Bt and a key K in
series. This is the primary circuit. The end C of the wire is connected to the
terminal M of a DPDT (Double Pole Double Throw) switch and the other terminal N
is connected to a jockey through a galvanometer G and a high resistance HR. The
cells whose emf ξ1 and ξ2 to be compared are
connected to the terminals M1,N1
and M2,N2 of the DPDT switch. The positive terminals of Bt,
ξ1 and ξ2 should be connected to
the same end C.
The DPDT switch is
pressed towards M1, N1 so that cell ξ 1 is included
in the secondary circuit and the balancing length l1 is found
by adjusting the jockey for zero deflection. Then the second cell ξ2 is included in the
circuit and the balancing length l2 is determined. Let r
be the resistance per unit length of the potentiometer wire and I be the
current flowing through the wire.
By including a rheostat
(Rh) in the primary circuit, the experiment can be repeated several times by
changing the current flowing through it.
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