This unit launches with a slow-motion video of a speaker as it plays music. In the previous unit, students developed a model of sound. This unit allows students to investigate the cause of a speaker’s vibration in addition to the effect.

Students dissect speakers to explore the inner workings, and engineer homemade cup speakers to manipulate the parts of the speaker. They identify that most speakers have the same parts–a magnet, a coil of wire, and a membrane. Students investigate each of these parts to figure out how they work together in the speaker system. Along the way, students manipulate the components (e.g. changing the strength of the magnet, number of coils, direction of current) to see how this technology can be modified and applied to a variety of contexts, like MagLev trains, junkyard magnets, and electric motors.

Calculating the dot and cross products when vectors are presented in their x, y, and z (or i, j, and k) components. Created by Sal Khan.

In this OLogy activity, kids learn how a compass works and why it will always point north. The activity begins with an overview that discusses our reliance on directions and how a compass works. Students are then given step-by-step, illustrated directions for creating a compass with a sewing needle, a small bar magnet, a small piece of foam, and other household items. The activity includes ideas about how to try out your compass.

Students will become familiar with the properties of magnets. They will design a data collection sheet to show where magnets are hidden in a closed box with their explanation of their findings. They will also design a game or activity using magnets and present their activity to the class.

Understanding the differences between the dot and cross products. Created by Sal Khan.

Sal shows that there will be a net torque on a loop of current in a wire. Sal shows that this net torque will cause the loop to rotate. Created by Sal Khan.

Sal shows that a commutator can be used in order to keep the loop of wire rotating in the magnetic field. Created by Sal Khan.

Sal finishes the explanation of how a commutator will allow a loop of wire to continue spinning in a magnetic field, thereby allowing it to work as an electric motor. Created by Sal Khan.

This course is a graduate level subject on electromagnetic theory with particular emphasis on basics and applications to Nuclear Science and Engineering. The basic topics covered include electrostatics, magnetostatics, and electromagnetic radiation. The applications include transmission lines, waveguides, antennas, scattering, shielding, charged particle collisions, Bremsstrahlung radiation, and Cerenkov radiation.
Acknowledgments
Professor Freidberg would like to acknowledge the immense contributions made to this course by its previous instructors, Ian Hutchinson and Ron Parker.

An emf induced by motion relative to a magnetic field is called a motional emf. This is represented by the equation emf = LvB, where L is length of the object moving at speed v relative to the strength of the magnetic field B.

This activity is a classroom and lab investigation of magnetism. Students gather results of experiments involving the forces of magnets. They use this data to develop their own experiments to test properties of magnets.

This resource provides a short reading section with experimental data and a few questions about the text. It was created with standardized assessment in mind and aligned with Next Generation Science Standards.

Play with a bar magnet and coils to learn about Faraday's law. Move a bar magnet near one or two coils to make a light bulb glow. View the magnetic field lines. A meter shows the direction and magnitude of the current. View the magnetic field lines or use a meter to show the direction and magnitude of the current. You can also play with electromagnets, generators and transformers!

Light a light bulb by waving a magnet. This demonstration of Faraday's Law shows you how to reduce your power bill at the expense of your grocery bill.

Light a light bulb by waving a magnet. This demonstration of Faraday's Law shows you how to reduce your power bill at the expense of your grocery bill.

How a current can be induced in a loop of wire by a change in magnetic flux.