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  • (a) Explain the principle of working of a potentiometer. (b) In a potentiometer, a standard source of emf 5V and negligible internal resistance maintains a steady current through the potentiometer wire of length 10m. Two primary cells of emf

(a) Explain the principle of working of a potentiometer.

(b) In a potentiometer, a standard source of emf 5V and negligible internal resistance maintains a steady current through the potentiometer wire of length 10m. Two primary cells of emf E1 and E2 are joined together in a series with (i) same polarity and (ii) opposite polarity. The combination is connected to the potentiometer circuit in each case. The balancing length of the wire in the two cases are found to be 700 cm and 100 cm, respectively. Find the values of emf of the two cells.

 

 

 
 
 
 
 

Answers (1)

a) 

The potentiometer is a device which does not draw current from the given circuit and still measures the potential difference. 

Working principle

For a steady current flowing through a uniform wire, the potential difference between any two points is directly proportional to the length of the wire between the two points

b)

 \\Potential\ gradient=\frac{V}{l}=5/10=0.5V/m\\E_1+E_2=7\times0.5=3.5V......(1)\\E_1-E_2=1\times0.5=0.5V.......(2)\\Solving\ (1)\ and\ (2)\\E_1=2V\\E_2=1.5V

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