# A student uses the circuit diagram of a potentiometer as shown in the figure(a) For a steady current I passing through the potentiometer wire, he gets a null point for the cell and not for  . Give the reason for this observation and suggest how this difficulty can be resolved.(b) What is the function of resistance R used in the circuit? How will the change in its value affect the null point?(c) How can the sensitivity of the potentiometer be increased?

Answers (1)

a)  Both   have the positive terminal connected at  A whereas negative terminal of  is connected to A. So null point is not obtained for cell 2

By interchanging the terminal of , the difficulty can be resolved.

b) The resistance R protects the galvanometer by reducing the current flowing through it. As the null point is obtained for zero galvanometer reading, change in resistance R does not affect the null point reading.

c) By increasing the length of the potentiometer the sensitivity can be increased.

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