Explain how waste energy is produced when an inefficient lightbulb converts electrical energy into radiant energy.

The First Law of Thermodynamics states that energy can neither be created nor destroyed, it can only be converted from one form to another. This may suggest that we could always convert energy to whatever forms we need without ever worrying about using up our energy resources.

However, not all the energy is converted into the desired form of energy (such as light). Although the quantity of energy is the same before and after conversion, the quality is different. An incandescent light bulb has a thin wire filament mounted inside it. When the bulb is turned on, an electrical current passes through the filament, heating it up so much that it emits light. The thermal energy that is produced by the light bulb is often called wasted heat, because it is difficult to use this form of energy to do work.

The energy that is wasted when a light bulb shines exemplifies the second law of thermodynamics that states that with each energy conversion from one form to another, some of the energy becomes unavailable for further use. Applied to the light bulb, the second law of thermodynamics says that 100 units of electrical energy cannot be converted to 100 units of light energy. Instead, of the 100 units that are used to generate light, 95 are needed to heat the filament. NOTE: There are other considerations with developing and using efficient conversion devices, such as costs and government subsidies.

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