In a practical Wheatstone bridge circuit as shown, when one more resistance of $100 \mathrm{\Omega }$ is connected in parallel with an unknown resistance $x$, then ratio $l_1/l_2$ become $2. l_1$ is balance length and $AB$ is a uniform wire. Then value of $x$ must be:

$R_1,R_2$ and $R_3$ are different values of $R$ and $A, B$ and $C$ are the null points obtained corresponding to $R_1,R_2$ and $R_3$ respectively. For which of the following the value of $X$ will be the most accurate:

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

In the circuit shown $P\ne R$, the reading of the galvanometer is same with switch $S$ open or closed. Then

The measurement of an unknown resistance $R$ is to be carried out using the Wheatstone bridge as given in the figure. Two students perform an experiment in two ways. The first students take $R_2=10 \mathrm{\Omega }$ and $R_1=5$$\mathrm{\Omega }$. The other student takes $R_2=1000 \mathrm{\Omega }$ and $R_1=500 \mathrm{\Omega }$. In the standard arm, both take $R_3=5 \mathrm{\Omega }$. Both find $R\mathit{=}\frac{{\mathit{R}}_{\mathit{2}}}{{\mathit{R}}_{\mathit{1}}}\mathit{,}\mathit{ }{R}_{\mathit{3}}=100 \mathrm{\Omega }$ within errors.

In a meter bridge, the point $\mathrm{D}$ is a neutral point (see figure).