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DC to AC to DC 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. 
  6. Students will know what an inverter is and what it does. 
Materials List

Group Supplies (2-4 Students)

  • AA battery holders – 10AA and in series for a 12 Volt battery pack(1 per group of 2-3) 
  • AA rechargeable batteries – 10 per group 
  • 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 taillights that charge with a USB. 
  • Male and female DC power plugs with pigtails (1 each per group) 
  • 12V female cigarette lighter plugs (to plug inverter in) with pigtails (1 each per group) 
  • Inverter – a small cigarette lighter inverter designed to be used in vehicles – usually limited  to 100W or so 
  • Student journals

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 5 of 7 / 2-4 hours

This lesson will continue to deal with efficiency of USB charging devices, but this time we will be using an inverter in order to create AC voltage from a battery pack, and then use a standard AC charger (what you would plug into the wall) to charge a USB device. Students will continue to use USB voltage/current meters to take readings on the charger-side of the circuit. After constructing these circuit components, students will measure the efficiency at which this inverter changes DC power back into DC power (in a DC-to-AC-to-DC conversion), and will collect the data in their journals using the self created tables in their science journals.

 

Off the Grid: Energy Transformations and Efficiency

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