Label the LED

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. It is important to know this 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.

LED legs are bent

1. It’s ok for the legs of the LED to be bent or reshaped
2. Reshape as necessary, replace if it breaks (it’s reasonable for them to break after moving the legs around a bunch)

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 backwards won’t have a negative effect on the LED, it just won’t turn on, so try it one way and if that doesn’t work, try flipping it around

1. Have students “use their observation skills” to tell you what they notice about the LED. Some good comments:

•  “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 wire is positive and the other wire 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 your students if they can think of anything else that has polarity. 3 main examples: batteries, magnets, and the earth. 

2 Labelling the LED allows the students to quickly identify which component is which. When you’re building your circuit later, having these components out and labelled allows you to quickly move through these steps.

3. Writing symbols for components makes it easier to draw. If there’s time, we draw the real component and show them how silly it looks versus just drawing the symbol. We also point out how long it takes to draw the real thing versus a symbol.

Thinkabit Companion Notebook: 

Students can draw a picture of the LED in their notebooks, making sure that one of the wires is longer than the other, and labeling the long side positive and the short side negative.