Question

Look at the Sankey diagram for a filament light bulb below. If the bulb is used in a desk lamp, what is the efficiency of the bulb?

Answer 1

Answer:

The question does not state how the answer is to be entered. I would use 10% because that is most common.

Explanation:

You are using 300 J of energy to get 30 J of light energy. The fact that you can account for the left over energy is not relevant.

Efficiency = Work Out / Work In

Efficiency = 30 J / 300 J  = 0.1

If you need this as a %, you can multiply by 100

Efficiency = 0.1 * 100 = 10%