The circuit shown in figure contains two ideal diodes $D_1$ and $D_2$. If a cell of emf $3 V$ and negligible internal resistance is connected as shown, then the current through $70 \Omega$ resistance, (in ampere) is

In determining the refractive index of a glass slab using a travelling microscope, the following readings are tabulated
(a) Reading of travelling microscope for ink mark $=5.123 \mathrm{~cm}$
(b) Reading of travelling microscope for ink mark through glass slab $=6.123 \mathrm{~cm}$
(c) Reading of travelling microscope for chalk dust on glass slab $=8.123 \mathrm{~cm}$
From the data, the refractive index of a glass slab is
In an experiment to determine the figure of merit of a galvanometer by half deflection method, a student constructed the following circuit.

He unplugged a resistance of $5200 \Omega$ in R . When $\mathrm{K}_1$ is closed and $\mathrm{K}_2$ is open, the deflection observed in the galvanometer is 26 div. When $K_2$ is also closed and a resistance of $90 \Omega$ is removed in S , the deflection between 13 div. The resistance of galvanometer is nearly
While determining the coefficient of viscosity of the given liquid, a spherical steel ball sinks by a distance $\mathrm{h}=0.9 \mathrm{~m}$. The radius of the ball $\mathrm{r}=\sqrt{3} \times 10^{-3} \mathrm{~m}$. The time taken by the ball to sink in three trails are tabulated as follows.
$$ \begin{array}{|l|l|} \hline \text { Trial No. } & \text { Time taken by the ball to fall by } \mathrm{h} \text { (in second) } \\ \hline 1 . & 2.75 \\ \hline 2 . & 2.65 \\ \hline 3 . & 2.70 \\ \hline \end{array} $$
The difference between the densities of the steel ball and the liquid is $7000 \mathrm{~kg} \mathrm{~m}^{-3}$. If $\mathrm{g}=10 \mathrm{~ms}^{-2}$, then the coefficient of viscosity of the given liquid at room temperature is