# Electricity Unit

ModelSim Electricity (previously known as NIELS) is a curricular unit consisting of a sequence of simulations authored in the NetLogo modeling environment. Most students find electricity a particularly hard topic to learn, whereas, most of them find electrostatics is relatively much easier. Learning Scientists suggest that this is due to the fact that we do not have access to electrical phenomena at a microscopic level – i.e., at the level of atoms and electrons. NIELS is designed to address this issue. Models in NIELS depict aggregate-level phenomena such as current, voltage and resistance as emergent – i.e., they arise due to simple interactions between many individual-level “objects” such as atoms and electrons. Using these models, students in middle school – college can actively explore and modify the relevant phenomena by interacting with the models at various levels – e.g., running glass-box experiments by changing values of variables on the user-interface and observing the resultant phenomena, and/or, by modifying and extending the underlying NetLogo model. No prior knowledge in electricity or programming in required.

We have succesfully tested NIELS in undergraduate, high school and middle school classrooms in the US and Singapore.

## Activities Overview

### 1.   Modeling Electrostatic Interactions

Students will use the Electrostatics model for this activity. The learning goals for this model are:

• Introduce students to Coulomb’s Law
• Introduce students to the connections between kinematics and electricity by using the same concepts (e.g, forces, potential and kinetic energy) in both the domains
• Students will also develop an understanding of how electrons’ acceleration is represented computationally (the dots spreading farther apart)

### 2.   Generating and Analyzing Electric Lines of Force

This model is furthers the investigation of motion of electrons due to electric forces

• Students are introduced to the notion of electric field lines field lines are “representations” of electric field – students should investigate “what do the field lines represent”?
• Students should be able to generate a continuous field by “spatially arranging” the polar charges in unipolar, dipolar and multi-polar fields
• Students can investigate the differences in motion of electrons in a “roughly” uniform field (i.e., by creating two walls of source-charges on either side of the model), and compare such motion with that of electrons in a non-uniform fields (make explicit the linear directional flow of electrons). Analyzing motion of test-electrons also further strengthens connection to kinematics

### 3.   Modeling Flow of Electrons Using Participatory Simulations

For this activity, students interact with a participatory simualtion in small groups of six or seven. The simulation models the filament of a light bulb from a micropscopic perspective. This simulation depicts two central mechanisms – flow and collisions – both of which are important for helping students understand resistance and current. The learning goals are as follows:

• students should be able to develop an understanding of the mechanism of resistance
• students should be able to develop an understanding of the relationship between collisions, heat and light
• students should start thinking about average and instantaneous current (may be through a class discussion towards the end of the activity)

### 4.   Measuring Current

In this activity, students focus on further deepening their understanding of how electric current can be measured, and how constancy of flow can be maintained in an Ohmic conductor. They will use both a computational model, as well as iteratively build and refine phyical models that will be analogous to the computational model. The learning goals for this activity include the following:

• Inventing multiple ways of measuring
• average current
• instantaneous current

Students should investigate how electric current depends on the relevant factors such as wire length, width, no-of-electrons, etc.

## Using the Electricity Unit in Your Classroom

The activities in the unit will be run on a WISE server, and each student will require access to a laptop or a desktop. Some of the activities require collaborative work. This includes both learning using virtual simulations collaboratively, as well as design-based activities that involve physical construction using materials that will be provided to the students. In both cases, collaboration will happen in small groups. Videos for supporting teachers will also be provided.