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Announcement

Announcement: Exam #1 grades are on E-learning. Average score: 6.28/10. Master copy of exam with 1 correct answer shared. Explore magnetic induction and fields. Learn formulas and examples. Check the link for more details.

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Announcement

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  1. Announcement • Exam #1 grades are posted on E-learning • Exam #1 average is 6.28 out of 10 (63%) • Master copy of exam #1 (correct answer 1) posted on E-learning

  2. Magnetic induction Magnetic flux density Magnetic field (strength) [B] = [F/IL] = Ns/Cm = Tesla *1 Tesla = 104 gauss F Length of the section in B-field B I FB = ILB

  3. B B  FB = ILB┴ I FB = IL(Bsin) • A net force on the loop • A net torque on the loop • A net force and torque • nothing, zip

  4. X X S N

  5. http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/mothow.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/mothow.html

  6. X X X X X X X X X DC Electrical Motor

  7. Example The earth’s magnetic field in Colorado is 0.59 G. It is directed at an angle of 67° below horizontal. Find the force on 5.0 m of an east-west wire carrying a westward current of 20 A. North-South wire?

  8. F S Are there ghosts in town? N In Colorado, B = 0.59 G = 5.9 x 10-5 T X 67 degree S N Force on a 5 m E-W wire carrying a 20 A west-bound current? F = ILB = (20 A)(5 m)(5.9x10-5 T) = 5.9 x 10-3 N X

  9. F F dF dL F I FB = ILBsin on a wire FB = qvBsin on a charge - F = I L B┴ dF = I (dL) B = (dQ/dt) dL B = dQ (dL/dt) B = dQ v B F = Q v B force on a moving charge Lorentz force

  10. Finding the Direction of Magnetic Force • The direction of the magnetic force is always perpendicular to both v and B • F = qvB sin • Fmax occurs when v is perpendicular to B • F = 0 when v is parallel to B

  11. Right Hand Rule • Hold your right hand open • Place your fingers in the direction of B • Place your thumb in the direction of v • The direction of the force on a positive charge is directed out of your palm • If the charge is negative, the force is opposite that determined by the right hand rule

  12. My Old TV

  13. Nam June Paik http://www.paikstudios.com/

  14. q q v v v v v q F F F F F q X x x x x X x x x x X x x x x X x x x x X x x x x X x x x x q F = q v B┴ Force by a magnetic field on a moving charge is always Perpendicular to the direction of motion. NO WORK DONE BY THE FIELD!!!

  15. B X x x x x X x x x x X x x x x X x x x x X x x x x r v FB = q v B Force by B-field q m This force causes a circular motion. Centrepetal force = FB Fc = mv2/r = q v B = FB r = mv/qB Since there is no work done by the field, in vacuum, The charge will make a circular motion forever!!!

  16. Bubble Chamber

  17. An object with +e charge And mass m kg r = 0.4 m B = 0.36 T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A univalent ion with mass m Came into the field region with Speed v = 6 x 105 m/s. Mass m? Mass spectrometer

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