Draw the schematic diagram of an electric circuit consisting of a battery of two cells of 1.5V each, three resistances of 5-ohm, 10 ohm and 15 ohms respectively and a plug key all connected in series.

This is the circuit having one plug key, one 5 ohm resistor, one 10 ohm resistor, one 15 ohm resistor and a battery of 2 cells each 1.5 V and everything is connected in series, so the battery is total of 3 V. As you can see there is open plug key, so, there is no current flowing in the circuit and hence we say that it is an open circuit.

As you can see it is the similar circuit as we have drawn the above one, but the only difference is in the plug key, this time the plug key is closed through which the circuit gets closed and gets completed connection, so, there is flow of current and remember the direction of flow of current is always in opposite direction of the flow of electrons, that is from positive to negative terminal conventionally.