PPT Slide

Current is charge in motion

• Charge, e.g. electrons, exists in conductors with a density, ne ne approx 1029 m-3

• “Somehow” put that charge in motion:
  • effective picture - all charge moves with a velocity, ve
  • real picture - a lot of “random motion” of charges with a small average equal to ve

• Current density, J, is given by J=qeneve
  • unit of J is C/m2sec or Ampere/m2
  • current, I, is J times cross sectional area
  • for 10 Amp in 1mmx1mm area, J=10+7 A/m2 , and ve is about 10-3 m/s

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