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

In a meter bridge or Wheatstone bridge for the measurement of resistance,the known and the unknown resistances are interchanged. The error so removed is

Two wires $A$ and $B$ of equal lengths are connected in the left and right gaps of a metre bridge. The null point is obtained at $40 \ cm$ from the left end. If the diameters of the wires $A$ and $B$ are in the ratio $3:1$,what is the ratio of the specific resistance (resistivity) of $A$ to that of $B$ (in $:$)?

$A$ resistance of $2\,\Omega$ is connected across one gap of a meter-bridge and an unknown resistance,greater than $2\,\Omega$,is connected across the other gap. When these resistances are interchanged,the balance point shifts by $20\,cm$. Neglecting any end correction,the unknown resistance is ................ $\Omega$.

During an experiment with a meter bridge,the galvanometer shows a null point when the jockey is pressed at $40.0 \ cm$ using a standard resistance of $90 \ \Omega$,as shown in the figure. The least count of the scale used in the meter bridge is $1 \ mm$. The unknown resistance is:

Explain the construction of a meter bridge used in the laboratory.