Question

Two cells of emf’s approximately $5V$ and $10V$ are to be accurately compared using a potentiometer of length $400cm$.

• A. The battery that runs the potentiometer should have voltage of $8V$.
  
• B. The battery of potentiometer can have a voltage of $15V$ and 𝑅 adjusted so that the potential drop across the wire slightly exceeds $10V$.
  
• C. "Potentiometer is usually used for comparing resistances and not voltages."
  
• D. "The first portion of $50cm$ of wire itself should have a potential drop of $10V$.
  

Answer 1

The correct option is B The battery of potentiometer can have a voltage of $15V$ and 𝑅 adjusted so that the potential drop across the wire slightly exceeds $10V$.


Given two cells of emf approximately $5V$ and $10V$ are compared.

To compare these cells accurately potential drop across potentiometer wire must be slightly greater than that of large emf, $10V$.

So, the battery can have a voltage of $15V$ and 𝑅 adjusted, so that the potential drop across the wire slightly exceeds $10V$.

Final answer: (b)