3. Energy Transformations

Most devices are energy converters. A toaster changes electrical energy into thermal energy. A speaker changes electrical energy into sound energy. A car engine changes chemical energy into motion and heat.

Useful energy is the energy you wanted. Waste energy is usually heat or sound that spreads into the surroundings.

Deep explanation. Energy transformations rarely produce only one output. A toaster changes electrical energy into thermal energy, but it may also produce light. A car engine changes chemical energy in fuel into motion, but much of the energy becomes heat and sound. A solar panel changes light energy into electrical energy.

The total energy is conserved, but the useful form may change. This is why devices can feel inefficient: energy has not disappeared, but some of it has spread into forms that are less useful for the intended task.

How GED® asks it. Look at the starting source and the final effect. Battery -> current -> motor motion is chemical to electrical to mechanical. Food -> muscles -> running is chemical to mechanical plus thermal. Sunlight -> plant sugar is light to chemical.

⚠️ Common misconception: waste energy is destroyed. It is still energy, just spread out in a less useful form.

💡 Tip: write energy chains with arrows.