Hello friends in this article we will know that direct current How to measure DC Potentiometer with potentiometer? And how is the DC Potentiometer measurement done with a DC potentiometer? And learn about many facts related to it.
DC Potentiometer measurement
Potentiometer basically measures the potential difference between two points but based on this it can be used to make many other measurements. Some of the common applications of potentiometer (DC Potentiometer measurement) are given below:
Determination of emf of a cell
Figure 16.30 is used to determine the emf of a cell with the help of a potentiometer. In this process the positive terminal of the cell whose emf E1 is connected to the positive terminal of battery E, then following the usual procedure, at point J Zero point is obtained.
At zero point, pd is the difference between points A and J. The emf of the cell, if the resistance of 1 cm wire AB is r and length AJ = l cm, then,
PD AJ = I (lr) or emf of the cell E1 = Ilr or E = kl where k (= I r) pd is the emf across a 1 cm length of wire AB. Then, E1 l Note that the potentiometer method is a zero method for determining emf.
Comparison of emf of two cells
Figure 16.31 shows the arrangement to compare the emfs E and E of two cells with the help of potentiometer. cells (E)1 and E2) is connected to the positive terminal of battery E. The negative term of the cells is attached to terminals 1 and 2 of the two-way key.
The common terminal 1 zero point J, connected to the jockey through the galvanometer G, is obtained with cell E alone. Now the first zero point is obtained at point J1 with cell E1 alone. Let’s say AJ1 = l1 E1 is l1.
Similarly, for E2 AJ2 = l2 then E2 l2
Then, the emf of the battery must be greater than the emf. E1 or E2 otherwise zero point will not be obtained. In addition, a shunt must be used with the galvanometer initially and removed near the zero point.
Determination of internal resistance of the cell
Figure 16.32 shows the arrangement of the battery to determine the internal resistance (r) of a cell of emf E. With the help of a potentiometer, the positive terminal of the cell is connected to the positive terminal of the battery. The negative terminal of the cell is connected to the jockey through galvanometer G. A resistance box R is connected to the cell through key K.
- The key K1 is closed and the current in the potentiometer wire AB is adjusted to a suitable constant value (say I) with the help of a rheostat. The setting of the rheostat should not be disturbed during use.
- Keeping the key K2 open, the position of the jockey is adjusted until the zero point is obtained, that is, the galvanometer reads zero. Let the point be obtained at point J on the potentiometer wire and the distance AJ1 = l1 then the emf of the cell E l1
- Now suitable resistance R is inserted and the key K2 is closed. Point is received on the potentiometer wire. Now the zero point corresponds to pd. V across the terminals of the cell If the zero point is obtained at point J2, and the distance AJ2 = l2 then, PD V l2
E/V = l1/l2
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