A torch runs on electricity, but you don’t have to plug it in. It carries its own electric current in a “package” – a battery.
A battery is made of layers of chemicals inside a metal container. When the torch is turned on, some of the chemicals in the battery break apart and eat away at the metal container. As this happens, some of the metal atoms leave the container and combine with the chemicals inside the battery.
As the metal atoms move away from the container, they leave some of their electrons behind. So the container gains electrons. And as the chemicals inside the battery break apart, they lose electrons.
Soon, there are more electrons in the container than there are inside the battery. Then the extra electrons in the container begin to move out of the battery. They travel through the bulb and back into the middle of the battery, where electrons are scarce. The push of these electrons is the current that makes your torch shine.
It may sound as if everything happens very slowly, but, as you know, it all takes place in an instant.
Picture Credit : Google