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A potentiometer wires has a length L and a resistance `R_(0)`. It is connected to a battery and a parallel resistance combination of R and S as shown in fogure. Find an exprssion for the potential gradient of the potentiometer wire.

Answer» Total resistance of potentiometer circuit
`R_(0) + (RS)/(R+S)`
Current in the circuit, `I = epsilon/(R_(0) + RS //(R +S))`
Potential differnce across the wire AB
`V = IR_(0) = epsilon/(R_(0) + RS//(R +S)) xx R_(0)`
Potential gradient, `K = V/L = (epsilon R_(0))/(L (R_(0) +( RS)/(R+S)))`
The emf of the test cell must be less than the total potential drop (V) across the wire AB. The positive terminal of test cell must be connected to end A of the wire.


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