In a potentiometer experiment, two primary cells are connected in series to support each other and then connected to oppose each other. The balance points are obtained at $4 \mathrm{m}$ and $1 \mathrm{m}$ respectively. The ratio of electromotive forces of the two cells is

In the following circuit a capacitor is charged from $q=0$ to $q=2\mathrm{\mu C}$ after switching on the circuit find energy delivered by the cell.

When will this capacitor get maximum charge, and what will be values of maximum charge and current at that state of the circuit?

For the given arrangement shown in figure. The switch is closed at $t=0$ The time after which the current becomes $2.5\mathrm{\mu A}$ is