The figure shows a circuit diagram of a Wheatstone bridge to measure the resistance $G$ of the galvanometer. The relation $\frac{P}{Q}=\frac{R}{G}$ will be satisfied only when

  

The potential gradient along the length of a uniform wire is $10 \mathrm{V} {\mathrm{m}}^{-1}$. The length of the wire is $1 \mathrm{m}$. What is the potential difference between two points on the wire separated by $25 \mathrm{cm}$?

In the shown arrangement of a meter bridge, if $AC$ corresponding to null deflection of galvanometer is $x$, what would be its value if the radius of the wire $AB$ is doubled?

The following figure shows cross-sections through three long conductors of the same length and material, with a square cross-section of edge lengths as shown. Conductor $B$ will fit snugly within conductor $A$, and conductor $C$ will fit snugly within conductor $B$. Relationship between their end to end resistance is