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Lecture Sixteen Physics 100 Fall 2012

Lecture Sixteen Physics 100 Fall 2012. Electric Motors. Announcements. Lab WILL BE HELD t oday and tomorrow as well as next Tuesday (Thanksgiving week). If you need to attend an earlier lab due to travel issues, please let me know today. Homework due Monday-posted.

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Lecture Sixteen Physics 100 Fall 2012

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  1. Lecture Sixteen Physics 100 Fall 2012 • Electric Motors

  2. Announcements • Lab WILL BE HELD today and tomorrowas well as next Tuesday (Thanksgiving week). If you need to attend an earlier lab due to travel issues, please let me know today. • Homework due Monday-posted. • Quiz on magnets and variables next Monday (Thanksgiving week). If you need to take it early (Friday) please send e-mail today.

  3. The Concept of a “Field” • In science a field is a collection of measurements of the same quantity over a region of space. • Common examples include temperature fields, elevation fields, magnetic fields and gravitational Fields.

  4. Magnetic Field • Amagnetic field is a collection of measurements across a region of space that indicates the relative strength of the magnetic force and the direction of the force on a north pole of a magnet placed there. • Thesymbolfor the magnetic field is B. The unitis the TeslaorGauss.

  5. The Earth Is a Big Bar Magnet

  6. Field lines go from north poles to south

  7. Current carrying wires are electromagnets. They produce magnetic forcesand therefore magnetic fields.

  8. Finding the direction of the field for a current carrying wire • The field lines for a current carrying wire are circles. To find the direction of the field, point your right thumb in the direction of the current. Curl your fingers and they will point in the direction of the field.

  9. What is the direction of the magnetic field at the x? x • Up toward the wire • Down away from the wire • Into the page • Out of the page • To the right i

  10. Magnets exert forces on one another.Sometimes this is a repulsive push, other times an attractive pull.

  11. Current carrying wires are electromagnets

  12. There is a magnetic force on a current carrying wire.

  13. Finding the direction of the force • Point your right fingers in the direction of the current. • Keeping your fingers pointed in the direction of the current, rotate your hand so that you can bend your fingers into the direction of the magnetic field. • Your outstretched thumb then points in the direction of the magnetic force on the wire.

  14. There is a magnetic force on a current carrying wire.

  15. What is the direction of the magnetic force on the wire? (The magnetic field due to the other magnet is downward) • Up toward the top of the page • Down toward the bottom of the page • Into the page • Out of the page • To the left north magnetic pole i south magnetic pole

  16. Electric Motors • An electric motor is a device that converts electrical energy into mechanical energy. • Electric motors use magnetic force to cause motion.

  17. A Simple Electric Motor

  18. Finding the direction of the force

  19. A Simple Electric Motor

  20. We will investigate electric motors in lab this week.

  21. We will investigate electric motors in lab this week.

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