Varying Emissivity by Color

Low power transformers are most commonly seen in the form of black boxes on chargers and power adapters, such as cell phone and laptop chargers. We tested the efficiencies of four such transformers and compared them to the EPA's requirements for its Energy Star program, to see if the transformers are up to par with standards. To test this we created and modified a four-outlet electrical receptacle, adjusting the resistance inside the circuit. We then found the input and output powers of the transformers to find their efficiency percentages. Statistical t-tests were then performed on these efficiency values, comparing them to the EPA's Energy Star standards. According to our test results, the average efficiencies of half of the transformers differed significantly from Energy Star requirements. We determined that low power transformers are on average 62% efficient, which is the guideline for Energy Star qualification.

Research Done By:

Michael Chan
Cousino High School

Joe Korolewicz
Cousino High School