Naval Postgraduate School
Dudley Knox Library
NPS Dudley Knox Library
View Item 
  •   Calhoun Home
  • Institutional Publications
  • Multimedia
  • Video
  • View Item
  •   Calhoun Home
  • Institutional Publications
  • Multimedia
  • Video
  • View Item
  • How to search in Calhoun
  • My Accounts
  • Ask a Librarian
JavaScript is disabled for your browser. Some features of this site may not work without it.

Browse

All of CalhounCollectionsThis Collection

My Account

LoginRegister

Statistics

Most Popular ItemsStatistics by CountryMost Popular Authors

Magnetic Forces and Magnetic Fields [video]

Icon
View/Open
Magnetic_Forces_and_Magnetic_Fields.mp4
Download
IconMagnetic_Forces_and_Magnetic_Fields.mp4 (37.49Mb)
Download Record
Download to EndNote/RefMan (RIS)
Download to BibTex
Author
Naval Postgraduate School Physics
Date
2015
Metadata
Show full item record
Abstract
Magnetic Forces and Magnetic Fields Hi. I’m Dr. Bruce Denardo here in the Physics Department of the Naval Postgraduate School in Monterey, California. When a charged particle moves through a magnetic field, a force on the particle can occur. This is the fundamental magnetic force. In this video, we will present a demonstration of the effect. In other videos, we will use the concept of the magnetic force to explain other demonstrations, including a jumping wire and a loudspeaker. 2. CATHODE RAY TUBE This is a cathode ray tube, which produces a beam of electrons. The beam is visible due to argon gas in the tube. The electrons are moving so fast here that gravity is negligible. Watch what happens when I bring a magnet near the beam. The beam deflects, which shows that there is a transverse force due to the magnet on the moving electrons. In general, any charged particle that is moving in a magnetic field will experience this fundamental magnetic force. The beam is horizontal outward. When the magnetic field points to the right, the beam bends downward. Switching the direction of the field by flipping the magnet switches the direction of bending. When the magnetic field points downward, the beam bends to the left. But, of course! We can think of this as just rotating the first demonstration clockwise by 90 degrees. Note that the beam always deflects perpendicular to both the magnetic field and the velocity of the electrons. Finally, there is no force when the magnetic field is parallel to the beam. The fundamental magnetic force law quantitatively accounts for our observations. The force is the charge times the vector (or cross) product of the velocity and the magnetic field. The force is perpendicular to both the velocity and the magnetic field, and the direction is given by the right-hand rule. The force is a maximum when the velocity and magnetic field are perpendicular to each other, and is zero when they are parallel. Let’s check the magnetic force law for the cathode ray tube in the case where the magnetic field points to the right. Using the right-hand rule, the force should be up, but the deflection is down! What’s wrong? Electrons have negative charge, which flips the direction of the force. So the magnetic force law does work here! 3. CONCLUSION A charged particle that is moving in a magnetic field can experience a force, which is the fundamental magnetic force. The force is given in general by the charge of the particle times the vector product of the velocity of the particle and the magnetic field. What if we have the common situation of a wire that is carrying an electric current? If the wire is in a magnetic field, there will in general be a force on the moving charges and thus a force on the wire. This leads to many demonstrations and applications. We will show some of these in other videos. It is important to remember that the physics behind these observations comes from the fundamental magnetic force law that can be demonstrated by a cathode ray tube and a magnet. Physics lecture demonstrations are always fascinating, and the quest for them never ends. This is the Physics Department of the Naval Postgraduate School, and I’m Dr. Bruce Denardo. Thank you.
Description
NPS Physics
 
 
Physics Demonstrations
 
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
URI
http://hdl.handle.net/10945/56276
Collections
  • Video

Related items

Showing items related by title, author, creator and subject.

  • Icon

    Magnetic force on a current carrying wire - Jumping wire physics demonstration [video] 

    Naval Postgraduate School Physics (2015);
    Magnetic Force on a current carrying wire Hi. I’m Dr. Bruce Denardo here in the Physics Department of the Naval Postgraduate School in Monterey, California. In another video, we demonstrated the fundamental magnetic force ...
  • Icon

    How Do Speakers Work? [video] 

    Naval Postgraduate School Physics (2015);
    How Do Speakers Work? Hello. I’m Dr. Bruce Denardo here in the Physics Department of the Naval Postgraduate School in Monterey, California. The purpose of a loudspeaker is to convert electrical energy into acoustic energy. ...
  • Icon

    Magnetic Forces on Moving Charges 

    Stevens, Mark; Koh, Ernest (2003-11-25);
    This interactive tutorial provides the practice to reinforce the concept of magnetic force of moving charges. The key concepts covered include: The direction of the resultant magnetic force is always perpendicular to the ...
NPS Dudley Knox LibraryDUDLEY KNOX LIBRARY
Feedback

411 Dyer Rd. Bldg. 339
Monterey, CA 93943
circdesk@nps.edu
(831) 656-2947
DSN 756-2947

    Federal Depository Library      


Start Your Research

Research Guides
Academic Writing
Ask a Librarian
Copyright at NPS
Graduate Writing Center
How to Cite
Library Liaisons
Research Tools
Thesis Processing Office

Find & Download

Databases List
Articles, Books & More
NPS Theses
NPS Faculty Publications: Calhoun
Journal Titles
Course Reserves

Use the Library

My Accounts
Request Article or Book
Borrow, Renew, Return
Tech Help
Remote Access
Workshops & Tours

For Faculty & Researchers
For International Students
For Alumni

Print, Copy, Scan, Fax
Rooms & Study Spaces
Floor Map
Computers & Software
Adapters, Lockers & More

Collections

NPS Archive: Calhoun
Restricted Resources
Special Collections & Archives
Federal Depository
Homeland Security Digital Library

About

Hours
Library Staff
About Us
Special Exhibits
Policies
Our Affiliates
Visit Us

NPS-Licensed Resources—Terms & Conditions
Copyright Notice

Naval Postgraduate School

Naval Postgraduate School
1 University Circle, Monterey, CA 93943
Driving Directions | Campus Map

This is an official U.S. Navy Website |  Please read our Privacy Policy Notice  |  FOIA |  Section 508 |  No FEAR Act |  Whistleblower Protection |  Copyright and Accessibility |  Contact Webmaster

Export search results

The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

A logged-in user can export up to 15000 items. If you're not logged in, you can export no more than 500 items.

To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.