1 / 26

EM3 Electromagnetism

EM3 Electromagnetism. Electromagnetism. Forcing a wire through a magnetic field produces (generates) a current in the wire Example: Generator Converts mechanical energy into electrical energy. generators.

travis
Download Presentation

EM3 Electromagnetism

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EM3 Electromagnetism

  2. Electromagnetism • Forcing a wire through a magnetic field produces (generates) a current in the wire • Example: Generator • Converts mechanical energy into electrical energy

  3. generators • Generators spin a bundle of wire attached to a motor through magnets causing current or electricity to be produced

  4. Electromagnetic induction (induced current) • Electromagnetic induction- a current is produced in a wire by passing a magnet near it • The magnetic field lines (flux) crossing the wire cause the electrons in the wire to move (electricity)

  5. Electromagnetic induction • Force is greatest when the charge moves perpendicular to the magnetic field • At other angles the force is less • The force is 0 when the charge moves parallel to the magnetic field

  6. Magnetic flux • Magnetic Flux ( Φ ) - The # of magnetic field lines passing through a given area • Magnetic Flux( Φ ) =BA

  7. Magnetic Flux • Where is the greatest concentration of magnetic flux lines? • Near the poles (ends)

  8. Magnetic Field • A current carrying wire placed in a magnetic field experiences a force • Example: Motors • Converts electrical energy into mechanical energy

  9. Second right hand rule • 1. Keep hand flat • 2. Thumb in the direction of the current • 3. Fingers in the direction of the magnetic field • 4. Palm in direction of the force • All are perpendicular to each other

  10. What determines the strength of the force? • 3 factors affect the magnitude of the force on a current-carrying wire placed in a magnetic field • 1. Strength of the magnetic field • 2. Amount of current (velocity) • 3. Length of the wire

  11. Mathematically • F=B I l • F=Force (N) • B=magnetic field strength (N/am) • I=Current in wire (a) • l=Length of the wire perpendicular to the field (m)

  12. example • A segment of wire .040 m long is perpendicular to the magnetic field inside a solenoid. When a current of 3.0 amps flows through the wire, it takes a force of 0.020 Newtons to balance the wire. What is the magnetic field inside the solenoid. F= B I L .020N = B (3.0 amps) (.040m) B = .17 N / amp m

  13. charge • The formula can also be written for any single charge moving through a magnetic field • F=Bqv • F=Force (N) • B=Magnetic field strength (N/am) • q=charge (C) • v=velocity of charge (m/s)

  14. When the charge is an electron • When not just any charge, but an electron • F=Bev • e=charge for an electron (1.6 X 10^-19 C)

  15. Example • An electron moves through a magnetic field of .20 N/Am at a speed of 300,000 m/s. What is the force on the charge due to this field? F = B e v F = .20 N/Am (1.6 x 10-19 C)(300,000 m/s) F = 9.6 x 10-15 N

  16. Voltage • Voltage-Energy needed to move a charge

  17. Motors • Helps explain how motors work • Motors convert electrical energy into mechanical energy

  18. Faraday’s law • Faraday’s Law- Voltage (current) induced in a wire is proportional to the rate of magnetic flux cutting across the wire • What happens when you increase voltage? • Increase magnetic flux (the # of magnetic field lines/area)

  19. Relative motion • Relative Motion-The movement of one object with respect to another object

  20. Lenz’s Law • Lenz’s Law-The current induced in a wire is in such a direction that its magnetic field opposes the changing field that induced it

  21. Equation • Emf = -B l v • Emf=electromotive force (volts) • B=Magnetic Field Strength • l=length of wire • v=velocity

  22. Example • A wire of length 50 cm is moving at a speed of 2.0 m/s perpendicular to a magnetic field of 0.75 N/A m. What emf is induced in the wire? Emf = -B l v Emf = - (.75 N/A m) (.50 m) (2.0 m/s) Emf = 0.75 Volts

  23. transformers • Transformers- A device to increase or decrease voltage • http://phet.colorado.edu/en/simulation/faraday

  24. transformers • N1/N2 = V1/V2 • N=number of turns of wire • V=voltage (volts)

  25. Transformers: example • If the primary coil having 5 turns of wire contains 20 volts, what is the voltage in the secondary coil having 10 turns? N1/N2 = V1/V2 5 / 10 = 20 / V2 V2 = 40 Volts

  26. Bell ringer • 1. A segment of wire 25 cm long is in a magnetic field of .75 N/A m. The force on the wire is 0.30 N. What is the current flowing through the wire? • 2. A charge (2.3 X 10^-15 C) moves through a magnetic field at 225,000 m/s. What is the magnetic field strength if the force is 4X10^-4 N?

More Related