This java application is a collection of five simulations designed to help learners gain a visual and mostly qualitative understanding of magnetic fields and magnetic induction. These simulations display the magnetic field surrounding a bar magnet (along with a compass), a bar magnet moving near a pickup coil (a coil attached to a light bulb or galvanometer), an electromagnet, a transformer, and a generator. Students can explore Faraday Induction of currents and voltages due to changes in magnetic fields.
Type of Material:
These simulations can be used for pre-class or interactive in-class demonstrations or for a virtual laboratory exercise.
A java-enabled web browser and Java Web Start is needed to run these simulations.
Identify Major Learning Goals:
After using these simulations students should be able to create a map of the magnetic field surrounding a bar magnet and an electromagnet, indicate similarities and differences between these two magnetic field sources, and explain the physical parameters that impact the magnitude and direction of the field created by an electromagnet. With the induction simulations, students should be able to explain the physical parameters necessary for magnetic induction of current and be able to predict the relative magnitudes and directions of those currents for different physical systems. Students should also be able to give a qualitative explanation of the operation of generators.
Target Student Population:
Introductory physics classes and/or laboratory at both the high school and college level. This could also be used for a middle school level physical science class.
Prerequisite Knowledge or Skills:
No previous knowledge is required, although previous exposure to fields and magnetic forces, which is usually the case in physics classes, will impact the student interactions with the simulations.
Evaluation and Observation
This collection of simulations includes many of the simple situations that demonstrate magnetic fields and induction: a bar magnet, current loops, transformers, and a simple generator. The student can use these to actively explore the properties of this physics by moving objects and observing both qualitative and quantitative measurements.
The simulations are very impressive in that any changes in the properties of the objects creates a correct response. The standard methods for inducing a current, such as moving a magnet or coil or changing the magnetic field of an electromagnet, work well. Other changes work as well. For example, in the Pickup Coil simulation, an abrupt change in the number of loops in the pickup coil will cause a resultant response in the volt meter or light bulb attached to the coil. Similar responses occur for an abrupt change in the voltage driving the current in a loop or changing the polarity of a magnet.
The objects in the simulation are quite realistic, giving students the indication that this is clearly reflecting real physical systems.
The simulation illustrates current as the movement of large spheres through wires. This may concern instructors, but research by the authors has shown this is not a problem for student understanding.
The Transformer simulation allows the two coils to pass through each other. This is one case where the objects are not completely physical.
Quantitative predictions can not, in general, be made.
Potential Effectiveness as a Teaching Tool
This simulation is very good at giving the learner a visual picture of how a changing magnetic flux can induce an electric current. It allows the user to move the magnets and coils themselves, exploring the physics. For example, students can discover that the speed at which the magnet moves into and out of the coil affects the size of the induced current. The ability to adjust the size of the magnetic field strength, the number of loops in the coil, and the area of the coil also allows the exploration of all aspects of the physics.
These simulations have very clear and physical properties, making them immediately accessible for students. The simulations mirror experiments that students are likely to do in a lab or see in a classroom demo. This means that they are ideal as either pre-labs or reviews.
Example lesson plans and curricular resources to compliment these simulations are available.
This simulation is focused on a specific topic in electricity and magnetism. PhET has other circuit simulations but currently there is no simulation of magnetic forces that might be useful to explain some aspects of induction.
Because of the qualitative nature of the simulations, including distances and areas, detailed quantitative explorations are not possible.
Ease of Use for Both Students and Faculty
The use of these simulations is intuitive. Users should have no difficulty grabbing items to move, changing sizes through sliders and buttons, and making measurements.
Help for using the simulations is not currently available, but is hardly needed.
Other Issues and Comments:
This is an excellent collection of applets focused on a specific physical topic.
Comments from Author:
We have found that students are remarkably good at exploring simulations very similar to how a scientist would. They observe and investigate letting their own questions guide their actions. We recommend focusing all your questions on the scientific concepts as opposed to specific sim type questions. For example, we find asking Can a magnet affect an electric current? How or why? is much more effective than explore the magnetic field slider and tell me what it does