In the given circuit, the internal resistance of the cell is zero. If $i_1$ and $i_2$ are the readings of the ammeter when the key $(K)$ is opened and closed respectively, then $i_1: i_2=$

In a meter bridge, the null point is located at 20 cm from left end of the wire when resistances $R$ and $S$ are connected in the left and right gaps respectively. If the resistance $S$ is shunted with $60 \Omega$ resistance, the null point shifted by 5 cm , then the values of $R$ and $S$ are respectively

The readings of the voltmeter and ammeter in the circuit shown in the diagram are respectively

When two identical batteries of internal resistance $1 \Omega$ each are connected in series across a resistor $R$, the rate of heat produced in $R$ is $P_1$. When the same batteries are connected in parallel across $R$, the rate of heat produced is $P_2$. If $P_1=2.25 P_2$, then the value of $R$ is