electric charge

• Electric Charges

  • Proton - Positively charged
  • Electron - Negatively charged
  • Neutron - No charge; neutral charge
• Electric Charges


  Determines the electric interaction and magnetic interaction between subatomic particles and other charged particles
• Electric Charges

  Affected by electromagnetism
• Electric Charges: '“like charges repel, unlike charges attract”'
• Electric Charges


  Represented by “q”
• Electric Charges

  SI Unit: Coulomb (C)
• 1 C = 6.242 x 10^18 e
• In an atom, the subatomic particles provide the net charge
• Electric Charges

  • Cation
  • Anion
• Materials


  • Conductors
  • Insulators
• Conductors are materials, such as metals, that allow the free movement of charges
• Insulators are materials, such as rubber and glass, that don’t allow the free movement of charges
• Charging by Friction

  1. Materials have different affinities for electrons

  2. When insulators are rubbed together, one gives up electrons and becomes positively charged, while the other gains electrons and becomes negatively charged
• Common examples of charging by friction include small shocks from a doorknob after walking on carpet with rubber-soled shoes and a balloon rubbed with hair sticking to a wall
• Common materials experimented on

  • Dry Hand
  • Leather
  • Glass
  • Human Hair
  • Nylon
  • Wool
  • Fur
  • Silk
  • Wood
  • Amber
  • Rubber
  • Polyester
  • Styrofoam
  • Polyurethane
  • PVC
• Charging by Conduction

  1. When a charged conductor makes contact with a neutral conductor, there is a transfer of charge

  2. Electrons are transferred between objects, leaving them both charged
• Charging by Induction

  1. Step 1: A charged rod is brought near an isolated conductor, polarizing it

  2. Step 2: The conductor is grounded to allow charge flow
• Electric Dipole


  A pair of point charges having equal magnitude but opposite sign that are separated by a distance
• Polarization


  Process wherein an electrically neutral body becomes polar by the rearrangement of its molecules
• Electric Forces, Electric Field and Electric Flux
• The Electrostatic Force is proportional to the product of the charges and inversely proportional to the square of the distance between them
• Charles Coulomb and Michael Faraday are notable figures in the study of electric forces
• A torsion balance measures the force between small charges
• The force depends directly on the magnitude of the charges and inversely on the square of the distance between them
• The force depends directly on the magnitude of the charges
• Electrostatic Force

  Fe = (9.0 x 10^9) * 5 x 10^-6 C * -8 x 10^-6 C / (0.04 m)^2 = -225 N
• The negative sign means force of attraction, but does not indicate left or right direction
• Fnet = Fleft - Fright = 360 N - 225 N = 135 N, to the left
• The Electric Force is like the Gravitational Force
• The electric force can be thought of as being mediated by an electric field
• E = FE/q
• If there is an electric force acting on an object having a charge, then the electric field at that point is given by E = Q/r^2
• Calculate the electric field that a test charge will experience if the distance from a source charge of 5.02 x 10^-13 C is 2.04 x 10^-3 m
• A charge of 3.0 x 10^-8 C experiences an electrostatic force of 6.0 x 10^-8 N. Compute the force per coulomb that the charge experiences
• Electric Field Lines begin on Positive Charges and end on Negative Charges
• Gauss's Law relates charge and the electric field
• The electric flux refers to the electric field lines that penetrate a given surface
• For a given uniform electric field E passing through an area A, the electric flux is defined as: E = ΦE/A
• One of the hypothetical applications of the concept of electric charges is on their role in pendulums bearing respective electric charge
• Find the charge on either of the ball in the hypothetical scenario provided