Phone Charger Efficiency

White board sketch of 12 V Car Charger for USB Device. Image Description under Featured Image Description Heading
Learning Goals

  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.
Materials List

Group Supplies (2-4 Students)

  • AA battery holders – 10-AA and 12-AA in series (1 per group of 2-3) 
  • AA rechargeable batteries – 10-12 per group 
  • Car cigarette lighter USB chargers – 1 per group, but each group should have a different brand for group comparisons 
  • USB current/voltage meters 
  • Multimeters (2 per group – one for voltage and one for current) 
  • ATC fuse holders (used for measuring current) 1 per group (see pics below) 
  • Cell phone or device that uses a USB plug for charging – students can bring in a USB  charging cord for their phone, or instructor can supply any USB charging device. I used LED bike tail lights that charge with a USB. 
  • Male and female DC power plugs with pigtails (1 each per group) 
  • 12V female cigarette lighter plugs with pigtails (1 each per group)

Important Links

Next Generation Science Standards

Next Generation Science Standards

  • HS-PS3-1. Create a computational model to calculate the change in the energy of one  component in a system when the change in energy of the other component(s) and  energy flows in and out of the system are known. 
Featured Image Description

Drawn on a white board in red marker 12 V CAR CHARGER FOR USB DEVICE underneath is a circuit diagram showing a ATC Holder (empty) to battery pack (12V) with DC female power plugs coming off of it to the right the male plugs connect to a female cigarette socket. A male cigarette plug (car charger) connects to the USB meter with power lines connecting off the bottom of the image. All junctions are labeled as listed in the description.

Lesson 3 of 7 / 2 hours

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.”

 

Off the Grid: Energy Transformations and Efficiency

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