Design Challenge: Lighting the Main Stage
Teacher Notes
NGSS Alignment: This task is aligned to the high school physical science performance expectation HS-PS3-3: Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.
Targeted Three Dimensions:
- Science and Engineering Practice (SEP): Constructing Explanations and Designing Solutions. Students design, evaluate, and refine a solution to a complex real-world problem (designing a stage lighting system) based on scientific knowledge, student-generated evidence, prioritized criteria, and tradeoff considerations.
- Disciplinary Core Idea (DCI): PS3.A: Definitions of Energy. Energy manifests itself in multiple ways, such as in motion, sound, light, and thermal energy. Students observe the conversion of electrical energy to light and thermal energy.
- Disciplinary Core Idea (DCI): PS3.D: Energy in Chemical Processes. Energy can be converted to less useful forms, such as thermal energy in the surrounding environment. Students observe energy loss in circuits.
- Disciplinary Core Idea (DCI): ETS1.A: Defining and Delimiting an Engineering Problem. Criteria and constraints include satisfying requirements such as mitigating risks (e.g., circuit breaker tripping) and are quantified (current $< 20\text{ A}$).
- Crosscutting Concept (CCC): Energy and Matter. Changes of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that system. Students map energy flows.
Evidence Statements Addressed:
- Using scientific knowledge to generate the design solution: Students develop a plan to convert electrical energy to light and thermal energy using the simulation. They identify scientific principles (Ohm’s Law, parallel vs. series circuits), identify energy forms, and explain the rationale for their design choice.
- Describing criteria and constraints: Students describe and quantify constraints, such as maximum current (20.0 A) to avoid tripping the breaker, the requirement for equal/full brightness across bulbs, and the requirement that breaking one bulb does not disable the system.
- Evaluating potential solutions: Students build and test both series (Track A) and parallel (Track B) setups against the constraints.
- Refining and/or optimizing the design solution: Students determine the optimal number of bulbs on the parallel track to maximize lighting without tripping the breaker.
Materials & Setup:
- Access to the Stage Lighting Simulator: Stage Lighting Simulator
- Estimated Time: 45-60 minutes
Part 1: Engage — The Stage Lighting Dilemma
You are the lead lighting technician for a local music venue. The main stage needs a major lighting upgrade. The venue manager wants the stage as bright as possible, but there’s a catch: the venue’s electrical system is old. The circuit breaker for the stage lighting is rated for a maximum of 20.0 Amps (A). If the total current goes over this limit, the breaker trips, and the entire stage goes dark mid-performance!
Additionally, stage lights are notorious for burning out or breaking during a show. The manager insists that if one light breaks, the rest of the stage must stay illuminated.
Discuss:
- Have you ever experienced a power outage caused by turning on too many appliances? What happened?
- If one light bulb burns out in a string of cheap holiday lights, often the whole string goes out. Why do you think that happens, and why would that be a disaster for a concert?
Part 2: Explore — Testing the Circuits
You have two options for wiring the new stage lights. Open the Stage Lighting Simulator and test both tracks to determine how they function.
Track A (Series Circuit) Testing:
- Turn the Main Power switch ON.
- Add bulbs one by one to Track A. Record the voltage, current, and power per bulb for 1, 3, and 6 bulbs in a data table.
- Observe the brightness of the bulbs as you add more.
- With 3 bulbs lit, click on one bulb to “break” it. What happens to the other bulbs? Click it again to fix it.
Track B (Parallel Circuit) Testing:
- Make sure Track A is off or ignore its readings. Focus on Track B.
- Add bulbs one by one to Track B. Record the voltage, current, and power per bulb for 1, 3, and 6 bulbs in your data table.
- Observe the brightness of the bulbs as you add more. How does it compare to Track A?
- With 3 bulbs lit, click on one bulb to “break” it. What happens to the other bulbs?
- Continue adding bulbs to Track B. What happens when you add 5 bulbs? 6 bulbs?
Sample Data Table
| Circuit Type | Number of Bulbs | Voltage per Bulb (V) | Total Current (A) | Power per Bulb (W) | Observations (Brightness/Breaks) |
|---|---|---|---|---|---|
| Track A | 1 | ||||
| Track A | 3 | ||||
| Track A | 6 | ||||
| Track B | 1 | ||||
| Track B | 3 | ||||
| Track B | 6 |
Part 3: Explain — Analyzing the Data
Use the data you collected to answer the following questions:
- Energy Conversion: In this system, electrical energy is being converted into what two forms of energy by the bulbs?
- Track A Analysis: What happens to the voltage available to each bulb and the total current as you add more bulbs in series? How does this affect the power (and brightness)?
- Track B Analysis: What happens to the voltage available to each bulb and the total current as you add more bulbs in parallel? How does this affect the power (and brightness)?
- Evaluating Constraints: Revisit the manager’s constraints:
- Constraint 1: The system must not draw more than 20.0 A.
- Constraint 2: If one bulb breaks, the rest must stay lit.
- Constraint 3: Bulbs should be as bright as possible (maximum power).
Which track (A or B) meets Constraint 2 and 3? Does it always meet Constraint 1? Explain.
Part 4: Elaborate & Evaluate — Designing the Final Array
Based on your findings, design the final lighting array for the stage.
Your Task: Write a proposal to the venue manager recommending a specific lighting setup. Your proposal must include:
- The Choice: State clearly whether you are choosing Track A (series) or Track B (parallel).
- The Layout: State exactly how many bulbs should be installed on that track.
- Scientific Rationale: Explain why you chose this track and this specific number of bulbs. Use evidence from your exploration (voltage, current, power data) and scientific principles (how parallel vs. series circuits distribute voltage and current) to justify your choice.
- Tradeoffs: Discuss any tradeoffs. For example, why can’t you install 6 bulbs on your chosen track, even if it would be brighter? What would happen, and why is that a risk?
- Energy Flow: Describe the flow of energy in your chosen system. Where is the electrical energy coming from, what forms is it converted into, and is any energy “lost” to the surrounding environment?