The PhET Interactive Simulations Project: Working to Increase Access to Interactive STEM Simulations [Part 1 of 2]


By Emily B. Moore


The PhET Interactive Simulations project ( at the University of Colorado Boulder develops a popular suite of free simulations (sims) for teaching and learning science and mathematics. This suite consists of over 150 interactive sims on topics in physics, chemistry, mathematics, earth science, and biology for students from elementary school to college. The PhET project impacts classrooms around the world with over 100 million sim runs per year, with sims available in 86 languages. In this article, we introduce PhET sims, describe features found in all PhET sims that support student engagement, and provide examples of how the sims can be used by teachers. In the second article, we will share how PhET is working to increase the accessibility of PhET sims worldwide, including the unique challenges and opportunities presented by highly interactive digital learning tools.

Teaching approaches that actively engage students with science and mathematics topics are known to be effective at improving student learning (Weiss, Pasley, & Smith, 2003) and improving student perceptions of science and mathematics (Kanter & Konstantopoulos, 2010; Swarat, Ortony, & Revelle, 2012). PhET sims are designed to be highly interactive and to support students to actively engage in learning. By providing a safe and effective environment to explore and experiment, students can learn foundational science and mathematics concepts with the sims (Moore, Chamberlain, Parson, & Perkins, 2014; Moore, Herzog, & Perkins, 2013; Podolefsky, Perkins, & Adams, 2010).

In this article, we will introduce three PhET sims: Balloons and Static Electricity, John Travoltage, and Energy Skate Park: Basics. We will use these sims as examples to demonstrate design features incorporated into all PhET sims, including features that provide opportunities for exploration, create a game-like environment, and scaffold learning. We will then describe a variety of ways teachers incorporate PhET sims into their courses. In the next article, we will share our progress in developing accessibility features for these specific sims capable of supporting students with and without disabilities in collaborative learning experiences.

Exploratory: Balloons and Static Electricity

Sim shows a bright yellow balloon (center), a large sweater (left), and a wall (right) each with several pairs of negative and positive charges.

Figure 1. Screenshot of the PhET simulation: Balloons and Static Electricity

The PhET sim Balloons and Static Electricity (Figure 1) can be used to address physics topics related to static electricity, including transfer of charge, attraction, and repulsion for students in middle grades up to introductory college levels. Interactive objects visible in the sim include a sweater, a balloon, and a wall. Charge is represented in the sim by blue circles labeled with a negative (-) sign, and red circles labeled with a positive (+) sign. As the balloon is rubbed against the sweater, negative charges are transferred from the sweater to the balloon, resulting in a net negative charge on the balloon and a net positive charge on the sweater. As the balloon is held against the wall, the negative charges on the wall are repelled by the negatively charged balloon. When the balloon is not being interacted with, it moves towards (i.e., attracts to) the sweater or the wall – depending on the net charge of all the objects. There is an option to remove the wall, and to explore using two balloons instead of one balloon. Also, the way that charge is shown onscreen can be changed from showing all charges to showing no charges or showing only the difference in charge.

As with all PhET sims, Balloons and Static Electricity is designed to be exploratory. By providing a small number of large, strategically placed, and brightly colored interactive objects, students are encouraged to move and change the objects in the sim – without requiring the sim to provide specific instructions on what students should do. As students interact with the objects, they are provided real-time feedback that provides information about how their interactions are impacting the objects. For example, as students rub the balloon on the sweater, the negative charges transfer from the sweater to the balloon, and when they “let go” of the balloon, the balloon attracts to (i.e. moves towards and “sticks” to) the sweater. These objects, interactions, and real-time feedback are designed specifically to support understanding of the relationships between transfer of charge, attraction, and repulsion. As students explore the interactive features within PhET sims, they are supported in developing an understanding of the underlying science or mathematics relationships represented in the sim.

Game-Like: John Travoltage

Sim shows John, standing on carpet next to door. John’s body contains many negative charges. His arm points up and is somewhat far from doorknob.

Figure 2. Screenshot of the PhET simulation: John Travoltage

The sim John Travoltage (Figure 2) can also be used to introduce topics related to static electricity across a wide range of age groups. In this sim, a character named John is standing on a carpet next to a door. John’s leg and arm are interactive, allowing students to rub John’s foot against the floor and collect negative charges. These negative charges are represented as blue circles with minus signs, and can be seen going into John’s body. As John’s hand is moved closer to the doorknob of the door, the static electricity can discharge – giving John a shock! When and how much John gets shocked depends on how close his hand is to the doorknob, and how much negative charge he has collected from the carpet. As students explore the relationship between the amount of charge and proximity to the doorknob, the use of the sim becomes game-like, as students playfully determine that by rubbing John’s foot on the floor and collecting a lot of charge, John can get shocked even when his hand is quite far from the doorknob.

Each PhET sim is designed to have a game-like quality, where the sim environment encourages students to ask questions (e.g., “Does John get shocked if his hand is far away?”), explore ways to find answers (e.g., changing the distance between John’s hand and the doorknob), and design experiments (e.g., find out how far away John’s hand can be while still getting shocked), all while feeling like they are playing a game with the sim.

One of the ways PhET sims achieve this game-like quality is by using connections to the real world where possible, while also providing representations and actions that are not possible in the real world. For example, in John Travoltage, the negative charge collected from the carpet is made explicit for students, but in the real world, although these charges are present, they are invisible. Making the negative charges a main focus of the sim, and making the charges explicit, provides an opportunity for students to explore the behavior of the negative charges and their relationships to a real world experience – getting shocked. In John Travoltage, students can use John to explore the experience of getting shocked by static electricity in unique ways, investigate relevant factors, broaden their understanding of their own experience of the world around them, and have fun at the same time.

Scaffolded: Energy Skate Park: Basics

Sim shows skater heading down left side of U-shaped track. A graph charts a small amount of kinetic and thermal energy and lots of potential energy.

Figure 3. Screenshot of the PhET simulation: Energy Skate Park: Basics, “Intro” screen

The sim Energy Skate Park: Basics (Figure 3) can be used to explore conservation of energy and concepts related to kinetic and potential energy, with students from middle grades up to introductory college levels. These concepts are scaffolded through the use of three different screens. The first screen, the “Intro” screen, opens with a “U”-shaped track with a skateboarder standing next to it. Students can drop the skater on the track, and the skater will move back and forth along the track, or even skate off the edge of the track onto the ground – depending on how the student has dropped the skater onto the track. There are options to:

  • change the shape of the track (to one of three different tracks available),
  • view changes in the skater’s kinetic and potential energy using a bar chart or pie graph,
  • overlay a grid onto the screen to help students reproduce experiments with the skater,
  • view the speed of the skater with a speedometer, and
  • change the mass of the skater with a slider.

Because of the design of the screen and the options provided, students focus on exploring the relationship between the motion of the skater, the change in energy and speed, and how the mass of the skater affects these (or not). The choice of track helps students explore these relationships in three particularly useful contexts.

In the next screen (not shown), the “Friction” screen, a new option is provided – a slider that allows students to control the amount of friction between the track and the skateboard. On this screen, sim use becomes focused on understanding the relationships between the motion of the skater, changes in energy and speed, and amount of friction.

In the third screen (not shown), the “Playground” screen, students are given the opportunity to build their own tracks to continue exploring motion, energy, speed, mass, and friction. A common game-like activity is for students to build a track that contains a loop, and to explore what combination of track height and friction is needed to allow the skateboarder to complete the loop without falling off the track.

As students use Energy Skate Park: Basics, their use is scaffolded through the design of the three screens. Each screen opens with a simple scenario, a single track and a skateboarder (or in the case of the “Playground” screen, a skateboarder in need of a track). By starting with this basic scenario, each screen supports students in focusing on a specific set of variables. In the “Intro” screen, the focus is on exploring energy, speed, and mass. In the “Friction” screen, the focus is on exploring energy, speed, and mass, plus friction. By providing the useful constraint of having three specific track scenarios to choose from, we ensure that students are engaging with three useful scenarios during their exploration. In the “Playground” screen, we relax this constraint and allow students to explore energy, speed, mass, and friction, using strategies developed in the other screens, but now in scenarios they create themselves. The scaffolding provided through the design of the sim supports students in intuitive, playful exploration, while ensuring that students are exploring useful scenarios as they develop their understanding.

Each of these design features – exploratory, game-like, and scaffolded – are part of every PhET sim and serve to support learning through active engagement. More information about our design approach, including more features found in PhET sims and an in-depth description of our approach to scaffolding can be found in the Research section of the PhET website (

Highly flexible – Teachers use PhET Sims in many ways

PhET sims can be used in many ways inside – and outside – of class (Moore et al., 2014). Some common ways teachers use PhET sims include:

  • Lectures – the teacher projects a PhET sim in front of the class, and uses the sim to illustrate specific points. This approach can vary from a quick 1-2 minute lecture supplement, to more extended use. For example, teachers can set up scenarios in the sim and ask students to predict what will happen next, or teachers can ask a series of questions about what will happen or has happened in the sim and discuss. Teachers can choose to have class discussions about some or all of the relationships represented in the sim. By using capabilities of the PhET sims to support exploration of productive scenarios, and provide real-time feedback, teachers can increase active engagement during their lecture time.
  • Guided-inquiry Activities – some teachers provide opportunities for students to use the sim themselves as part of class. Student sim use is often facilitated through a guided-inquiry activity – a digital or paper resource containing guiding questions and a place for students to record ideas and findings. Students can work individually, or in pairs or larger groups. Typically, teachers will facilitate the class during guided-inquiry activities by roaming the room and answering questions, and have specific “check points” where they bring the class together to discuss questions and findings so far. At the end of a guided-inquiry activity, teachers often take a few minutes to summarize the key points from the activity and discuss any further questions or insights from students. Through the use of guided-inquiry activities, teachers can use PhET sims to support students in learning through active engagement.
  • Homework Assignments – teachers can assign activities that use PhET sims as homework assignments. Activities could be as simple as prompting students to explore a particular PhET sim and find two ways to create a specific outcome in the sim. This type of assignment can be particularly useful for preparing students prior to a class where they will be more formally introduced to the topic. Homework assignments with sims can also be more involved, with sim use supporting students in answering a series of open-ended or multiple choice questions. In this approach, teachers can use PhET sims to increase opportunities for students to actively engage with the content, even outside of class.

All of these styles of sim use can be implemented in-person or online. The PhET website contains many ideas and resources for using PhET sims to teach science and mathematics concepts, and to support active engagement by students, including teacher-submitted classroom activities and video guides with classroom examples (

Sim Accessibility and Inclusion

Many aspects of PhET sims can support inclusive learning opportunities for students. For example, the sims can be run on a wide-range of devices, including: desktops, laptops, tablets, and mobile phones. This level of cross-device compatibility enables classrooms and students with diverse technology access to make use of the sims. Each sim is translatable, with sims available in 86 languages. The highly-visual features of the sims can support students with certain learning disabilities, as well as any student who particularly benefits from visual learning resources. Furthermore, due to the flexibility in how the PhET sims can be used by teachers, and the wide range of devices on which the sims run, PhET sims support the learning of science and mathematics in diverse learning scenarios including activities in a face-to-face classroom, or learning activities embedded into learning management system, or activities that combine both. In Part II, we will share our efforts to expand the inclusivity of the sims even further, with the addition of a variety of accessibility features that can support students with mobility, sensory, or learning disabilities, as well as students without disabilities, in learning with sims. To explore our complete suite of sims, and to find more resources about using PhET sims, please visit the PhET website (


Emily B. Moore is Director of Research and Accessibility for the PhET Interactive Simulations project at the University of Colorado Boulder. Dr. Moore conducts research across middle school and undergraduate levels on topics including simulation design, student use of simulations, and teacher facilitation strategies with simulations. She also leads research and development efforts to increase the accessibility of PhET simulations, which includes recent work in the design of auditory description, keyboard navigation, and sonification to support non-visual access to simulations.


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Moore, E. B., Chamberlain, J. M., Parson, R., & Perkins, K. K. (2014). PhET Interactive Simulations: Transformative Tools for Teaching Chemistry. Journal of Chemical Education, 91(8), 1191–1197.
Moore, E. B., Herzog, T. A., & Perkins, K. K. (2013). Interactive simulations as implicit support for guided-inquiry. Chemistry Education Research and Practice, 14, 257–268.
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Published September 2017