Question

1. a lightbulb takes in 60 j of electrical energy and converts 18 j of that energy into light. what is the efficiency of the lightbulb?

Explanation:

Step1: Recall efficiency formula

The formula for efficiency $\eta$ is $\eta=\frac{\text{useful output energy}}{\text{input energy}}\times100\%$.

Step2: Identify input and output energy

The input energy is $E_{in}=60\ J$ and the useful output energy (light energy) is $E_{out}=18\ J$.

Step3: Calculate efficiency

$\eta=\frac{18}{60}\times 100\% = 0.3\times100\%=30\%$

Answer:

$30\%$