What form of energy that is not useful is being released from the flashlight when it is on?

Answer 1

Incandescent light bulbs, including those used in traditional flashlights, generate heat by running an electric current through a wire filament. This heats the filament to incandescence, which generates light.

But it also generates a lot of heat; up to about 80% of the energy is released as heat rather than light. Sometimes the heat is a useful side effect; for example, in a terrarium or over a buffet heat lamp, or in a cold room in the winter. But generally the heat is wasted energy.

More modern flashlights, and many modern light fixtures, use Light-Emitting Diodes, or LEDs. These release about 60% of their energy as light. There's still some waste heat, but a much higher proportion of the energy consumption is light rather than heat.

An intermediate development called "Compact Fluorescent Lights", or CFLs, were a major disappointment; they saved some energy but were hideously expensive, short-lived, and contained hazardous chemicals if they were broken.

Answer 2

Mechanical energy is not released. Flash lights include heat and light energy.

Answer 3

Thermal energy