In a wheatstone's bridge, three resistances $$\mathrm{P}, \mathrm{Q}$$ and $$\mathrm{R}$$ are connected in the three arms and the fourth arm is formed by two resistances $$S_1$$ and $$S_2$$ connected in parallel. The condition for the bridge to be balanced is

If a current flowing in a coil is reduced to half of its initial value, the relation between the new energy $$\left(E_2\right)$$ and the original energy $$\left(E_1\right)$$ stored in the coil will be

The Kirchhoff's current law and voltage law are respectively based upon the conservation of

A moving coil galvanometer is converted into an ammeter, reading upto $$0.04 \mathrm{~A}$$ by connecting a shunt of resistance '$$3 \mathrm{r}$$' across it and then into an ammeter reading upto $$0.8 \mathrm{~A}$$, when a shunt of resistance '$$r$$' is connected across it. What is the maximum current which can be sent through this galvanometer if no shunt is used?