What is the efficient energy of a light bulb with an electrical energy input of 100J, light energy output of 10J and a heat energy of 90J?

1 answer

To find the efficiency of a light bulb, you can use the following formula for efficiency:

\[ \text{Efficiency} = \frac{\text{Useful Output Energy}}{\text{Input Energy}} \times 100% \]

In this case:

  • Useful Output Energy (light energy output) = 10 J
  • Input Energy (electrical energy input) = 100 J

Plugging these values into the formula:

\[ \text{Efficiency} = \frac{10, \text{J}}{100, \text{J}} \times 100% \]

Calculating this gives:

\[ \text{Efficiency} = 0.1 \times 100% = 10% \]

Thus, the efficiency of the light bulb is 10%.