If each resistance in the figure is $9 \Omega$, then the reading of the ammeter $(A)$ is

The area of cross-section of a copper wire is $4 \times 10^{-7} \mathrm{~m}^2$ and the electrons per cubic metre in copper is $8 \times 10^{28}$. If the wire carries a current of 6.4 A , then the drift velocity of the electrons ( $\mathrm{in} 10^{-3} \mathrm{~ms}^{-1}$ ) is

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