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Explain the use of potentiometer for comparison of e.m.f. of two cells. |
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Answer» Solution :Potentiomter. A potentiomter consists of a uniform and long wire stretched on a wooden board. Its ENDS are connected to battery B through rheostat `R_(h) and ` an ammter. Ells whose e.m.f.s are to be compared are connected as shown in the FIGURE. Priciple. the potential drop across any PORTION of the wire, is directly proporrtional to the length of that portion of wire, provided wire is uniform and a constant current flows through it.  Comparison of e.m.f..s of two cells. The positive of `E_(1) and E_(2)` are connected to a terminal P where the positive of auxiliary battery B is connected. negative are connected to a galvanometer through two way key. the other end of galvanometer is connected to a jockey which can slide over the wire. circuit is closed FIRST by putting the key between 1,3 and then between 2,3. the length of the wires, `l_(1) and l_(2)` for which there is no deflection in the galvanomter is noted. Now `E_(1) prop l_(1) and E_(2) propl_(2)` or `E_(1)=kl_(1) and E_(2)=kl_(2)` Dividing, `(E_(1))/(E_(2))=(l_(1))/(l_(2))` |
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