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Instructions
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  1. Lay your LED on a piece of paper.
     
  2. Circle and label the LED.  
     
  3. Draw the symbol for the LED next to the LED.
     
  4. Draw a plus sign (+) next to the long leg and a minus sign (-) next to the short leg.

 

STEM Connections

LED stands for Light Emitting Diode. An LED is made with a semiconductor that converts 'electrical energy' to 'light energy' when electric current flows through it in one direction.

Just like batteries have positive and negative terminals, LEDs have positive and negative sides. This is important because electric current can only flow through the LED in one direction, from the positive to the negative side. Electrical components that affect how electric current flows based on what direction it is placed into the circuit are said to have polarity. In this activity, you will also be using metal wire. The metal wire does not have polarity because electric current can travel through it in either direction.

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Implementation
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At the Thinkabit Lab, we ask students to describe and label the components of an LED using symbols, making it easier for them to identify components when they build a circuit. We do the following:

  1. Rather than simply tell students that one wire of the LED is longer and one is shorter, ask students to “use their observation skills” to describe the components of an LED. Students should respond:

    • “There are 2 wires.” –Yes! We can think of those 2 wires like its hands or arms. That is the LED’s way of connecting to other things and letting the electricity flow through it, just like in the human circuit activity.

    • “One wire is longer/shorter than the other.” –Yes! The wires are different lengths to signify that one is positive and the other one is negative. The longer wire is positive and the shorter wire is negative. This is called polarity (when there is a difference between positive and negative). Ask students if they can think of anything else that has polarity. There are three main examples: batteries, magnets, and the earth.

  2. Ask students to label the positive and negative side of the LED.

  3. Ask students to use symbols for components. If there is time, have students draw the actual component (LED) and explain that a symbol is easier to draw and more practical to use, instead of the real component.

 

If you are using the Thinkabit Lab Notebook:

Students can use the picture of the LED in their notebooks on page 13, labeling the long side positive and the short side negative.  They can also write toward the bottom of page 13 where it says "LED:" on the first line: long leg (+) and on the second line: short leg (-).  This will be helpful when completing the LED circuit.

LED:  long leg (+)                                 
           short leg (-)                                 

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Troubleshooting
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LED legs are bent

  1. Bend and reshape the legs of the LED, as necessary.

  2. Replace the LED if it breaks. It is normal for LEDs to break after repeated reshaping of the legs.

Can’t find the long/short leg of LED

  1. If the legs of the LED have been reshaped too much, it can be difficult to figure out which leg is short or long.

  2. Placing the LED in backward won't have a negative effect on the LED, it just won't turn on, so you can try it one way and if it doesn't work, flip it around.

Instruction Category
Video