In a simple circuit, why does the bulb glow when you close the switch ?

When does a bulb glow ?

Does the bulb glow in acids ?

The given figure shows a simple circuit consisting of a bulb and a switch. On closing the switch, the bulb will

The given figure shows a simple circuit consisting of a bulb and a switch. On closing the switch, the bulb will

In the circuit shown in figure: Would any of the bulb glow when the switch is in the'OFF' position?