In the circuit if current flowing through $R_2$ is $0.5\mathrm{A}$ and through $20\mathrm{\Omega }$ is $1\mathrm{A}$ ,then resistance ${\mathrm{R}}_1$ and ${\mathrm{R}}_2$ are respectively​​​​​​​

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The potential difference between points $A$ and $B$ of adjoining figure is

As the switch $S$ is closed in the circuit shown in figure, current through it is

Find the equivalent resistance between the terminals $X$ and $Y$.

The total current supplied to the circuit by the battery is

In the figure shown, the current flowing through $2R$ is

In the circuit shown, the current through the $4 \mathrm{\Omega }$ resistor is $1 \mathrm{A}$ when the points $P$ and $M$ are connected to a $\mathrm{DC}$ voltage source. The potential difference between the points $M$ and $N$ is