How can the ammeter reading calculated without voltage value given?

Dear student,

Although the voltage reading is not given, it is given that the current in ammeter’s branch is 27mA immediately when key is closed. When key is just closed, the capacitor behaves like a conducting wire and the current from the source divides int the inverse ratio in the 2R and 3R resistors.Hence current from the source is 45mA. Hence the voltage can be calculated.

A long time later, the capacitor is fully charged and behaves like an open circuit. In that case the R and 2R resistors come in series and 4R and 3R also come in series. For the calcultated voltage of the source, the current in the ammeter in this case can be calculated.