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Aim: How can we explain the 3 rd left hand rule of magnetism?

Aim: How can we explain the 3 rd left hand rule of magnetism?. Do Now: How will the current flow?. To the left. 3 rd Left-Hand Rule. Used any time you have a charge moving through a magnetic field.

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Aim: How can we explain the 3 rd left hand rule of magnetism?

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  1. Aim: How can we explain the 3rd left hand rule of magnetism? Do Now: How will the current flow? To the left

  2. 3rd Left-Hand Rule • Used any time you have a charge moving through a magnetic field. • When current is placed perpendicular to magnetic field, a force will be produced on the wire.

  3. Place thumb in direction of current, and fingers pointing in direction of magnetic field. Your palm will point in the direction the force pushes.

  4. Which direction is the force? Up N S Current

  5. Describe the motion of the moving charge • To figure out the force on a positive charge, use the right hand (or opposite from negative charges) • This is how Jay can smash particles together • http://www.youtube.com/watch?v=bEvLK11jdJ8 • The resultant of the velocity and the force can produce circular motion

  6. Remember… • Moving charges create magnetic fields. • Your left-hand rules • These concepts revolutionized the world

  7. Force on a Current Carrying Wire **The x is a cross product – this means the wire and field must be perpendicular to use this formula F = IlxB F = force (N) I = electron flow (A) l = length of wire (m) B = Magnetic Field strength (Tesla = T = N/Am)

  8. Example Problem The current flowing in a 2.0 m wire is 100 A. The wire is placed in a magnetic field of 3.0 x 10-3 T such that it is oriented perpendicular to the field. Calculate the force experienced by the wire. F = IlxB F = 100 A(2.0 m)(3.0 x 10-3 T ) F = 0.6 N

  9. Force on an Electron An electron entering a magnetic field experiences a force similar to that on a wire (proton would go in the opposite direction). Since F = IlB and I = q/t Then, F = qlB/t, and l/t = v Then the force on any charged particle is F = qvB

  10. Mass of an Electron 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 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 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 e- p Since a particle is free to move, upon entering a magnetic field, it will constantly change directions in response to the force so, it goes in a circle

  11. Mass of an Electron Because the electron moves in a circular path the force can also be considered a centripetal force, so F = qvB = mv2/r Therefore, q/m = v/Br 1897: charge to mass ratio (q/m) was determined by J.J. Thomson 1909-1913: charge of an electron was determined by Millikin with his oil drop experiment Mass of electron was then determined with q/m

  12. What will happen? x S N S N x x x x The wire will spin This is a motor Fingers – field Thumb – current Palm – force Axis of rotation

  13. Electric Motor Converts electrical energy to mechanical energy Motor Demo

  14. What will happen? x S N S N x x x x Current will be generated This is a generator Fingers – field Palm – force Thumb - current Axis of rotation

  15. Generator Converts mechanical energy to electrical energy Generator Demo

  16. This is what is happening Proton Aurora Forms from Reconnection Event AURORAS • Known as the northern lights • Electrons from violent storms on the Sun enter the Earth’s magnetic field • The electrons collide with gases in the Earth’s atmosphere • Color depends on the type of atoms and molecules struck This is what you see

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