Question

Derive the mathematical expression for the principle of a potentiometer.
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Answer 1

Potentiometer

Potentiometer is used for the accurate measurement of potential differences,current and resistances it consists of 10 metre long uniform wire of manganin or constantan stretched in parallel rows each of 1 metre length,on a wooden board.The two free ends A and B are brought to the same side and fixed to copper strips with binding screws.A metre scale is fixed parallel to the wire.A Jockey is provided for the making contact.

ε = Irl.

Since I and r are constants,ε ∝l. The emf of the cell is directly proportional to the balancing length.