Current Electricity and Electrical InstrumentHard
Question
In the potentiometer arrangement shown, the driving cell D has emf e and internal resistance r. The cell C, whose emf is to be measured, has emf ε/2 and internal resistance 2r. The potentiometer wire is 100-cm long. If balance is obtained at the length AJ = l.
Options
A.l = 50 cm
B.l > 50 cm
C.Balance will be obtained only if resistance of AB is ≥ r.
D.Balance cannot be obtained.
Solution
Potential gradient x = 
× 
Where R = resistance of potentiometer wire.
= xl
= 
× 
l
l =
⇒ l > 50 cm. Ans.
∵ Balance length should be less than or equal to 100 cm
l ≤ 100 ⇒
≤ 100 ⇒ R ≥ r Ans.
× Where R = resistance of potentiometer wire.
= xl = × ll =
⇒ l > 50 cm. Ans.
∵ Balance length should be less than or equal to 100 cm
l ≤ 100 ⇒
≤ 100 ⇒ R ≥ r Ans.Create a free account to view solution
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