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 \varepsilon _{1}and not for \varepsilon _{2} . 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)
S safeer

a)  Both \varepsilon _{1}  have the positive terminal connected at  A whereas negative terminal of E_{2} is connected to A. So null point is not obtained for cell 2

By interchanging the terminal of \varepsilon _{2}, 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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