Potential difference between $A$ and $B$ is .............. $V$.

What is the equivalent resistance between $X$ and $Y$ in the given circuit?

Find the value of current $i_1$ for the circuit shown in the figure. (in $, A$)

In the network shown,the cell of emf $E$ has internal resistance $r$ and the galvanometer shows zero deflection. If the cell is replaced by a new cell of emf $2E$ and internal resistance $3r$,keeping everything else identical,then:

Four resistors $A, B, C$ and $D$ form a Wheatstone bridge. The bridge is balanced when $C = 100 \ \Omega$. If $A$ and $B$ are interchanged,the bridge balances for $C = 121 \ \Omega$. The value of $D$ is: (in $\Omega$)

The potential difference between points $C$ and $D$ of the electrical circuit shown in the figure is (in $V$)