Academic journal article The Science Teacher

Using Colorful Light-Emitting Diodes to Engage Students in the Study of Electric Circuits: Teaching Electricity and Engineering with LEDs

Academic journal article The Science Teacher

Using Colorful Light-Emitting Diodes to Engage Students in the Study of Electric Circuits: Teaching Electricity and Engineering with LEDs

Article excerpt

When learning about electricity, students are typically asked to complete a simple circuit involving a battery, wire, and lightbulb. This activity can be enhanced by adding discussion and discourse (Yang 2008) and can take on a unique final form in the case of "The Friendship Detector" (Cox 2012). In such electrical circuit activities, the completed circuit is usually confirmed by a glowing incandescent bulb. This article describes circuitry lessons using light-emitting diodes (LEDs) instead. These hands-on exercises help students better understand electricity by

* building multiple circuits,

* demonstrating their knowledge of how the electrical energy changes with each new circuit and configuration,

* and applying what they have learned by engineering an authentic and useful electrical device that performs a specific task.

Teachers can connect these activities to aspects of the Next Generation Science Standards (NGSS) (NGSS Lead States 2013) (Figure 1).

How do LEDs work?

Light-emitting diodes are used in many consumer electronics products such as televisions, computers, and smartphones, and for good reason: LED arrays are 75-80% more efficient than traditional incandescent bulbs (U.S. Dept. of Energy 2012).

While incandescent bulbs produce light with a glowing metal filament, and compact fluorescent bulbs (CFLs) produce light when electrons interact with mercury and phosphorus in tubes, LEDs emit light when electrons pass between semiconductor materials inside the bulb. This is called electroluminescence. When electricity is applied, semi-conductor materials containing different compounds emit light at various wavelengths, producing a variety of colors (Edison Tech Center 2013). LEDs are now commonly available in red, green, blue, yellow, orange, purple, pink, and white.

FIGURE 1

Connections to the Next Generation Science Standards and A Framework for K-12 Science Education.

HS-PS3 Energy

* Performance Expectation HS-PS3-3: Design, build, and refine a device that works within given constraints to convert one form of energy to another form of energy.

* Disciplinary Core Idea PS3.A: Definitions of Energy: At the macroscopic scale, energy manifests itself in multiple ways, such as in motion, sound, light, and thermal energy.

* Science & Engineering Practices: Planning and Carrying Out Investigations, Developing and Using Models, Constructing Explanations and Designing Solutions.

* Crosscutting Concepts: Energy and Matter: Changes of energy... in a system can be described in terms of energy flows into, out of, and within that system.

[FIGURE 2 OMITTED]

These small electrical devices are safer, less expensive, and more durable than incandescent bulbs and many other electrical elements used in science classrooms, and LEDs are easy to work with.

Lesson 1: Building LED circuits

Students work with two 1.5 V AA batteries, two wires, and an LED. I begin by asking them for ideas for how these materials might be arranged to create an electric circuit. Then they experiment with different configurations, working in pairs or small groups so there are enough hands to help position the batteries, wires, and LEDs that make up the circuit. Chances are that one or more students will have some experience with these materials and can help inexperienced students. Give students time to arrange the circuit materials in various configurations until some successfully light the LED (Figure 2). Safety note: Inexperienced students may inadvertently short-circuit the batteries with the wires in an attempt to complete their circuit. This can harm the battery and may cause the battery and wire to heat up.

Some students will find that their LED in a proper closed circuit will not glow. They need to reverse the polarity of the LED or the circuit and realize that diodes only allow current to flow in one direction; i. …

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