Why does a torch bulb glow only when the switch is turned on?

Correct Answer: Because the switch completes the circuit, allowing current to flow

Explanation:

An electric circuit requires a closed, unbroken loop of conducting material for electric current to continuously flow from one terminal of a cell (battery) to the other. This flow of current powers devices such as a torch bulb.

When the switch is in the OFF position, the circuit is open (incomplete), leaving a gap in the conductive path. Because air is an insulator, current cannot jump across the gap, and the bulb stays off.

When the switch is turned to the ON position, it closes the gap by connecting the conducting wires together. This completes the circuit, providing a continuous path for electric current to flow through the filament of the bulb, causing it to heat up and glow.