In a meter bridge the point $D$ is neutral point as shown in the figure.

Assertion $(A):$ In a meter bridge experiment, null point for an unknown resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same $p$ as before by decreasing the value of the standard resistance.

Reason $(R):$ Resistance of metal increases with increase in temperature.

Explain how value of unknown resistor can be obtained by using meter bridge.

A wheatstone bridge is used to determine the value of unknown resistance $X$ by adjusting the variable resistance $Y$ as shown in the figure. For the most precise measurement of $X$, the resistances $P$ and $Q$:

In a meter bridge experiment, initially the jockey is at null point. Now resistance $R_1$  $\&$ $R_2$ is interchanged. Shift in the position of jockey is  ……………. $cm$