Question

The potentiometer works on the principle that at constant temperature, the resistance of a wire is proportional to its

• A. Length
• B. Area of cross section
• C. Material density
• D. None of the above

Answer 1

The correct option is A Length

If the hint was not obvious enough, it’s the LENGTH.
The potentiometer wire is of uniform cross section and made of a uniform material throughout so as to keep its resistivity constant.
As we already know the well-established relationships, $R=\frac{\rho l}{A}andV=iR$, the potential drops/rises uniformly across the length of potentiometer because resistance is directly proportional to the length of wire.