A student finds some information about energy-saving light bulbs. (a) A 30W light bulb uses 600J of electrical energy in a certain period of time . In that time, it produces 450 J of light energy. The rest of the energy is wasted. (i) Calculate the energy wasted by the light bulb in this period of time. Wasted energy= J (1)

Question

A student finds some information about energy-saving light bulbs. (a) A 30W light bulb uses 600J of electrical energy in a certain period of time . In that time, it produces 450 J of light energy. The rest of the energy is wasted. (i) Calculate the energy wasted by the light bulb in this period of time. Wasted energy= J (1)

Answer 1

Wasted energy = 600 J – 450 J = 150 J

Answer 2

This question relates to the conservation of energy principle, which states that energy cannot be created or destroyed, but only changed from one form to another. This is frequently represented in energy efficiency calculations, where the energy inputted into a system and the energy output from the system are compared to determine how much energy was transformed usefully (in this case into light), how much was 'wasted' (often being transformed instead to unuseful heat), and wherein the total energy remains the same.In this specific case, we're formulaically calculating the amount of energy that has been wasted in this transformation in an electrical light bulb using the following:Wasted energy = Total Energy input – Useful Energy output.

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