Electric Energy Transfer Investigation - Day 4
Lesson 9 of 13
Objective: Students continue an investigation of electric energy transformations.
Reminder about Projects
Student projects, demonstrating their understanding of the Conservation of Energy, are due next class so today I spend a few minutes reminding students about the project expectations. Though they received a rubric with the assignment, today's reminder boils down the expectations to just a few simple ideas.
I show this slide on the board:
I share with my my students the universality of these expectations. Students are encouraged to be creative in their choice of a final product (animation, slide show, poster, children's book, etc.) so they need to know how I'll assess these different kinds of submissions. No matter what kind of project they may have picked, I will look for their ability to provide their audience with appropriate background information and rich examples, delivered with clear and sound logic and reasoning.
The assignment itself is very conceptual in nature. I want students to adopt an audience (say, middle-school science students) and target them for their explanation of the conservation of energy (HS-PS3-2). The assignment provides all students an opportunity the chance to step away from computational work and to creatively address the concept of energy conservation.
Before continuing with the investigation of electric energy transformations, I provide a brief discussion of some common needs. As one of the goals of the investigation is to compare the electric energy provided with the "other" energy created (sound, light, heat, etc.), all teams need to be able to calculate the electric energy being provided by their power sources.
I show the following slide on the board:
As the power supply is continuously providing energy to the stations' distinct elements, it is more convenient to measure the number of electrical joules per second ("watts") supplied by the power source. Instead of energy, therefore, teams will need to calculate the power on the electrical side of their station. The graphic shows a split between what is common to all teams (the electric side) and what is distinct (a light bulb is shown in the graphic, but this could be a buzzer, a heater, etc.). I instruct the students to calculate power based on the power supply voltage (V) and the current out of the supply (I). Furthermore, I reassure them that our practice has been to record the voltage and current settings for each trial. As a result, this new information simply requires one simple, additional calculation based on that data.
On this fourth day of the investigation, students teams are wrestling with different needs; in addition, all teams are truly engaging in many, if not all, of the NGSS Science and Engineering Practices.
The emphasis of today's work is planning and carrying out an investigation (practice #3). In addition, many teams are developing and using models (practice #2) or using mathematics and computational thinking (practice #5). For example, the team investigating light energy from a light bulb is beginning to create a model in their minds about how electrical energy is converted into light and how the brightness measurement (in "lux") can be converted into power. Their work is a blend of lab work, Internet research, and conversations with their teammates and me as they try to resolve problems and collect valid data.
Students continue this work for most of the rest of this lesson. With about five minutes left in class, I prompt them to clean up their stations and return equipment to the storage area.
Here is a sample of an ongoing student investigation:
Here, students recount the difficulties of light station, but remain buoyant: