Find the equivalent resistance between $A$ and $E$ (resistance of each resistor is $R$).

In the circuit shown, current through $25\mathrm{}\mathrm{V}$ cell is

The equivalent resistance between $\mathrm{A}$ and $\mathrm{B}$ in the network in figure is

In the part of a circuit shown in figure, the potential difference $(V_{\mathrm{G}}-V_{\mathrm{H}})$ between points $\mathrm{G}$ and $\mathrm{H}$ will be

What resistor should be connected in parallel with the $20 \mathrm{\Omega }$ resistor in branch $ADC$ in the circuit shown in figure so that potential difference between $B$ and $D$ may be zero?