Torches help us to see by producing light energy. The energy starts as chemical energy in the batteries. Inside the batteries the chemicals react together to produce electricity. This electrical energy is then changed to light energy by passing it through a bulb.
A light bulb is a small, thin piece of strong wire inside a glass container. The air inside the glass container has been removed. When each end of the wire inside the bulb is connected to a supply of electrical energy the electricity makes the piece of wire glow very brightly, so producing light.
A torch is a convenient way of producing light energy. One or more batteries are contained inside the body part of the torch. The batteries are connected through a switch to a bulb. When the switch is turned on the series circuit is completed and so the bulb will light.