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