Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer. The value of the unknown resistor $R$ is …………. $\Omega$

The resistance per centimeter of a meter bridge wire is $\mathrm{r}$, with $\mathrm{X}\  \Omega$ resistance in left gap. Balancing length from left end is at $40 \mathrm{~cm}$ with $25\  \Omega$ resistance in right gap. Now the wire is replaced by another wire of $2 \mathrm{r}$ resistance per centimeter. The new balancing length for same settings will be at

A meter bridge set up as shown to determine end correction at $A$ and $B$. When a resistance of $15\ \Omega$ is used in left gap and of $20\ \Omega$ in right gap, then null point comes at a distance $42\ cm$ from $A$. When these resistances are interchanged null point comes at a distance $57\ cm$ from $A$. Values of end corrections are

In order to measure the internal resistance $r_1$ of a cell of emf $E$, a meter bridge of wire resistance $R_0=50 \Omega$, a resistance $R_0 / 2$, another cell of emf $E / 2$ (internal resistance $r$ ) and a galvanometer $G$ are used in a circuit, as shown in the figure. If the null point is found at $l=72 cm$, then the value of $r_1=$ . . . . $\Omega$

When Wheatstone bridge is said to be in balanced condition ?