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699 B

Electric Force, Field, and Potential

Summary

  • Measured in capacitance (C=\frac{Q}{\Delta V}), value fixed by physical build C=\kappa \epsilon_0\frac{A}{d}
  • Field between plates is uniform except near edges. E_C=\frac{Q}{\kappa \epsilon_0 A} (equal to \frac{\Delta V}{d})
  • Charged particle between plates feels constant force. Projectile with constant accel.
  • Stored energy written as: U_C=\frac{1}{2}Q\Delta V=\frac{1}{2}C(\Delta V)^2=\frac{Q^2}{2C}.
  • Adding dielectric raises capacitance by factor of \kappa, sets up induced field inside dielectric that opposes plate field.
  • On AP exam, only parallel plate capacitors required, edge effects ignored unless stated otherwise.