What is the energy efficiency of a light bulb that gives you 30 units of usable energy for every 100 units of energy put in to it?
a. 0.3
b. 3
c. 30

Explanation:

Given parameters:

Energy output = 30units

Energy input = 100units

problem:

Energy efficiency of light bulb:

Solution:

 Efficiency is given as:

    Efficieny = \frac{energy_{output} }{energy_{input } x100

   Efficieny = x 100 = 30%