Magnetic Levitation II: Magnet accelerates
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A neodymium disk magnet is levitated above a high-temperature superconductor. An electric current is passed through the magnet causing it to begin to rotate. Students can measure the final angular velocity, the time interval during which the current is applied, and the amount of current.
Instructor NoteWhen teaching with this video, direct students to the student video library, which provides student access to all videos without links to instructor materials and solutions.
This video can be used during an introduction to rotational dynamics where students apply Newton's Laws to rotating objects. The disk accelerates from rest beginning when the switch is closed and current begins to flow. When the switch is opened, the disk spins at a constant angular speed with very low friction. Students can measure the final angular velocity of the disk immediately after the switch is opened, and the time interval when the switch is closed.
Here is some useful information about the magnet:
- manufacturer's specifications
- mass: 73.9 grams
- diameter: 4.45 +/-0.01cm
This video can also be used to explore the force exerted on a current-carrying conductor in a magnetic field. In this case, the current-carrying conductor is the levitated magnet. Since there is a strong field inside the magnet, the force is exerted on the magnet, causing a torque and angular acceleration.