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In a potentiometer experiment why is it necessary ot used a long wire? Length and resistance of a potentiometer wire are 4 m and 10Omega respectively. It is connected to a cell of emf 2 volt. Another cell when joined to this potentiometer and null point is measured at 250 cm. Find out the emf of the second cell. |
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Answer» Solution :In different measurements using a potentiometer, the ratio `(L)/(L)` often comes in the WORKING formula. Here, L = length of the potentiometer wire, and l = length at which the null point is obtained . This ratio `(l)/(L)` is NATURALLY very accurate if both l and L are sufficiently large. So, a long wire is used in a potentiometer experiment. l = 250 cm = 2.5 cm , L = 4m , emf of the potentiometer cell, `E_(0)`= 2V So. the emf of the second cell = ` (l)/(L)E_(0) = (2.5)/(4) xx 2 = 1.25`V |
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