Physics Ch 16

• What is equal to the negative of the change in pot energy ?


  Work done by a conservative force
• Work is done when?

  The charge moves from A to B
• Work and Potential Energy

  WAB = Fx Δx =q Ex (xf – xi)
• Potential Energy


  ΔPE = - WAB = - q Ex x
• Force


  Fx =q Ex
• SI unit of energy 


  Joules (J)
• The electric potential difference ΔV

  ΔV = VB – VA = ΔPE / q
• Potential Difference 


  ΔPE = q ΔV
• SI unit of potential difference

  V = J/C
• Uniform electric field


  ΔV = -Ex ΔX
• Unit of electric field

  N/C = V/m
• What is a characteristic of field only?

  Electric Potential
• What is the characteristic of the charge field system?

  Electric Potential Energy
• The potential created by a point charge q at any distance r from the charge is

  V = Ke q/r
• What is the work required to bring q2 from infinity to P without acceleration is q2V1 equal to?


  The potential energy of the two particle system?

  PE = q2V1 = ke q1q2 / r
• PE is positive when?

  the Chargers have the same sign
• PE is negative when?


  The charges have different signs
• Capacitor


  A device used in a variety of electric circuits
• What is capacitance (C) of a capacitor is defined as?


  the ratio of the magnitude of the charge on either conductor (plate) to the magnitude of the potential difference between the conductors (plates)
• Capacitor consist of two parallel plates each has area (A)


  C = epcilon 0 A/d
• Capacitance


  C =Q/ 🔼V
• Capacitance unit


  Farad (F), 1F = 1C / V
• Gauss’ Constant

  Epcialon 0 = 8.85 x 10^-12 Permittivity of free space
• The relationship between capacitance and distanc?


  inversely related C = Epilcon 0 A/d
• The relationship between capacitance and change of V

  Inversely related C = Q/ Change of V
• When connected in parallel, each capacitor has the same potential difference


  • Δ V = Q/Ceq

  • Δ V1 = Δ V2 = Δ V
• The charge stored on each capacitor is then


  • Q1 = C1 (Δ V)

  • Q2 = C2 (Δ V)
• Capacitors in Series


  The equivalent capacitance of a series combination is always less than any individual capacitor in the combination.
• Capacitors in a series combination store the same charge


  Q = Ceq (change of V)
• The charge stored on each capacitor is then


  • Q1 = Q2 = Q
• When connected in series, the potential difference across each capacitor is


  • V1 = Q1/C1 • V2 = Q2/C2