Phone Charger Efficiency (Lesson 3)

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Brett McFarland
Intended Grade Level(s):
Estimated Activity Length:
2 hours
Learning Goal(s):

1. Students will use multimeters to measure voltage and current in circuits. 2. Students will use collected data and be able to make power calculations from this data. 3. Students will also be able to calculate efficiency from their power calculations. 4. Students will be able to compare efficiencies in order to identify the circuit that is most efficient. 5. Students will be able to make circuits from a diagram and vice versa.

Relevant Common Core Standard(s):
Relevant NGSS PE:

This is part of the Off the Grid Unit. In this lesson students will explore the concept of efficiency, and how to take data in order to calculate the efficiency of various cell phone or USB charging circuits. They will complete this process by using a combination of multimeters hooked into ATC fuse holders as well as USB current/voltage meters, collecting the Power-in and Power-out measurements for these circuits. This knowledge will pull from the initial lessons focusing on electrical units and measurement-taking processes and will be recorded in the journals they have been working with. Students will also be introduced to circuit diagrams, or “schematics.” 

Science Kit Material(s) Used


Other Material(s) Used

AA rechargeable batteries and holders, car cigarette USB charger, USB current/volt meter, ATC fuse holders, USB-powered device, Male and female DC plugs with pigtails, 12 V female cigarette lighter plugs

Thumbnail Image

Car Charger Schematic