Electrostatics

Charge.

• Some things have a positive charge and others have a negative charge.
  • Opposite charges attract each other.
  • Like charges repel away from each other.
  • Charged objects attract neutral (uncharged) objects
• Contact:
  • Movement/transfer of electrons between objects.
• e is the charge of a proton.
  • -e is the charge of an electrons.
• The coulomb (C) is a unit of charge.
  • 1C ~= (6.24)(10^18)(e) is a coulomb in terms of e.
  • e ~= (1.60)(10^(-19)) C is e in terms of coulombs.
  • A coulomb is the amount of charge transferred by a 1A current in 1s.
    • 1A refers to 1 ampere, a unit of current.

Coulomb's Law.

• _F(e) =(k _ |q(1) * q(2)|) / r^2*
  • F(e) is electrostatic force. Units is Nm^2 / C^2
  • q(1) and q(2) are the magnitudes of the 2 charges.
    • If q(1) and q(2) has same signs, repelling force.
    • If they are different signs, attractive force.
  • k ~= 9 * 10^9

Electroscope questions for test.

Ohm's Law.

• V = IR
  • Voltage (V)
    • electric potential
    • PE per unit charge
    • measured in Volts (V) which is J/C
  • Current (I)
    • change per unit time
    • measured in C/s aka amperes (A)
  • Resistance (R)
    • how much charge flow impeded
    • denoted by Ω

Power.

• P = VI
• P = RI^2