AI Tutor
Rub your hands together as fast as you can for five seconds.
Notice how your palms suddenly feel warm, even though all you did was move them?
That warmth happens because of an energy transformation—the process where energy changes from one form into a different form within a system.
A system is any group of connected parts that work together to do a job, like your body, a toaster, or a bicycle.
What happens when we look at a device with multiple connected parts, like a handheld flashlight?

Tracing a Flashlight System

When you slide the switch on a flashlight, chemical energy stored inside the battery changes into electrical energy flowing through the wires.
Once that electrical energy hits the bulb, it transforms into light energy that brightens the room, along with a little bit of thermal energy that warms the bulb.
In the 1840s, English scientist James Joule used spinning paddle wheels in water to prove that motion transforms directly into heat, helping scientists discover that energy never vanishes—it simply changes form.
It is easy to think energy 'disappears' when a toy stops moving or a battery runs down, but it never actually vanishes.
Every bit of that stored energy simply transformed into heat, sound, or light that spread out into the air around it.