The Large Hadron Collider at CERN

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The Large Hadron Collider at CERN
1200 dipole magnets
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The LHC dipole magnets
With an ingenious design intense electric
currents two electric fields are produced in
opposite directions to keep protons in orbit
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The larger R, the greater v (and energy) LHC
R4.4 Km
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Partons (quark and gluons) in proton collide at
high energies and produce heavy particles
Proton
Proton Remnants
Emc2
Proton
Parton
Parton
Parton-Parton Interaction
Proton Remnants
Search for the Higgs boson Origin of Mass in the
Universe
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Is the LHC Dangerous?
No, its not
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Energy Spectrum of Cosmic Rays
Earth is bombarded everyday with cosmic
particles with huge energy, much larger than the
proton collisions at the LHC
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CERN the birth place of the internet
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Physics 202, Lecture 14

• Todays Topics
• Faradays Law (Ch 31)
• Change of Magnetic Flux and Emf (e)
• Lenzs Law
• Faradays Law of Induction

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Electromotive Force (emf, e)

• Electromotive force, emf, is a measure of the
  voltage that can be provided by a source.
• For a given device, if a charge Q passes through
  that device, and gains an energy U, the net emf
  for that device is the energy gained per unit
  charge, or U/Q.
• emf is not a force, it has a unit of volts
• sources of emf
• chemical process (battery)
• change of magnetic flux
• semiconductors..
• e.g. battery
• notice that emf has a direction
• emf may exist even if no current.

e 1.5V
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Demo Emf and Change of Magnetic Flux
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Lenzs Law

• The emf due to change of magnetic flux tends to
  create a current which produces a magnetic field
  to compensate the change of original magnetic
  flux.
• Lenzs law is a convenient way to determine the
  direction of the emf due to magnetic flux change.
  

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Demo Eddy Current
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Formulation of Faradays Law

• The emf induced in a circuit is proportional to
  the time rate of change of magnetic flux through
  the circuit.
• Notes
• Circuit any closed path
• does not have to be
• real conducting circuit
• The path/circuit does not
• have to be circular, or even planar

nominal direction of e
B
q
A
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Direction of Induced emf

• egt0, same as nominal direction
• elt0, opposite
• Note that the nominal direction
• of e and the direction of vector A
• follows right hand rule

nominal direction of e
B
q
A
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Methods to Change Electric Flux

• Change of FB? emf
• To change FB
• Change B ? emf produced by an induced E field
• Change A ? motional emf
• Change ? ? motional emf
• Combination of above