  ## Overview

Students represent their circuits by making drawings, and then compare their drawings with others’. They are often hard to interpret. To solve this problem, students learn to use standard circuit symbols and conventions to represent their circuits. Then they learn to light a Light-emitting Diode (LED) from two batteries in series, and construct new circuits using circuit diagrams as guides.

• Chart of Standard Circuit Symbols (see below).

## Materials

• Circuits from Lesson 2
• Additional AA Batteries,coin batteries, Red LEDs, tape, foil, rubber bands

## Procedure

1.      Coin batteries and LEDs.  Provide each student with a coin battery and a red LED.

• Make the LED light
• Use a switch to turn the LED off.
• Working with a partner, light two LEDs

2.      Circuit drawings. Pose the challenge:

Suppose someone else wanted to make a circuit just like the one you made. Make a drawing of it so they will know what to do.

3.      Gallery walk. Post the circuit drawings, and allow everybody to examine them. Then ask:

• How are these drawings different?
• What problems would someone have in following them?

Elicit the observation that different students used different symbols for representing the same items. If someone doesn’t know what your symbol represents, they will not know how to make what you made.

4.      Symbols. Standard symbols provide a way to give information in a very small space. If everyone agrees on what the symbols mean, there is no need to explain them each time. Brainstorm examples of how symbols are used. Then introduce the standard circuit symbols that work the same as other symbols. They save a lot of space, and are easy to understand, once everybody agrees on what they mean. Here is an activity to practice interpreting rules and symbols.

5.      Comparing diagrams with drawings. Ask each student to make a diagram of the same circuit they drew earlier, this time using the standard symbols and rules. Then conduct another Gallery Walk to compare the two representations for each circuit:

• How do they compare?
• What makes one of them easier to follow?

6.      Using circuit diagrams. Circuit diagrams tell you how to make new circuits. The Lesson 3 worksheet presents two activities where students construct circuits from circuit diagrams.

7.      Outcomes.

• Diagrams are different from drawings. A drawing tries to show what things look like, but a diagram reveals its structure. Electrical diagrams use a common set of symbols and rules, which make circuit operation clear.
• Standard diagrams make circuits easier to understand and troubleshoot.
• Electrical diagrams are also useful for trying out circuit ideas, before actually building the circuits. They are excellent design tools.
• Word-wall words: LED, symbol, standard symbol, polarity, diagram, design, chart of standard circuit symbols.