Students have made motor-driven cars. Now they add a sub-system of lights or a subsystem of a horn to enhance their cars. The resulting car may have three electrical sub-systems: motor, lights and horn. Students may also add decorations or even a reversing switch.

Coin batteries, lights and buzzers. Provide these components. Ask students to get the LED’s to light and the buzzers to sound. Each one can work from a single coin battery, and some will work in combination. Encourage students to explore the combinations:

- What do you need to do to make the light come on?
- How can you get more than one LED to light up from a single coin battery? What combinations will work?
- How can you make the buzzer sound?
- How can you operate the buzzer and a light from the same coin battery?

Brainstorming ideas for Improving your Ride. Once students have learned to make circuits with LED’s, buzzers and coin batteries, encourage them to think about how these could improve their cars:

- How could you use these to make lights and horns for your car?
- How would you turn the lights and horn ON and OFF?

Provide worksheets for students to begin thinking about these questions. Remind them to use standard schematic symbols and diagrams to show their ideas. Some decisions students will need to make are:

* How many lights will you need?

* Will the lights run off the same battery as the motor, or a different battery?

* What kind of switch will you use? Where will you put it?

* Will you also add a horn? If so, what circuit will it be in? How will you control it?

* What changes will you need to make to the car body and circuit to include lights and/or a horn?

Working on circuits for lights and horns: Provide students with materials, so they can begin working on their improved cars. Much of this work is likely to be self-directed, and students should be able to help one another. Intervene only when necessary to help students avoid frustration. Here are videos for making different circuits and switches:

There is a worksheet to structure the planning of additional circuits. It may be downloaded below.

When students have completed their work, they write an Instruction Manual for their improved cars. The worksheets for the Instruction Manual may also be downloaded below.

**Outcomes:**

A system can include more than one circuit.

- Designing a system include making a plan as well as circuit diagrams.
- Different kinds of loads have different requirements.
- Every circuit needs its own switch.

Several questions arise in this lesson. Here are some of them, with links to answers.