ELECTROSTATICS

mass of particle

electron

9.11 x 10^-31 kg

proton and neutron

1.67 x 10^-27 kg

quantization of charges

Q=Ne

e=1.602 x 10^-19 C

conservation of charges

  1. electric charge occur naturally
  1. electric charges not created nor destroyed
  1. electric charge just transferred from one body to another

law of conservation of charges

method of transferred charges

the net charges of a closed system never changes

conduction

induction

grounding

Coulomb's law

F=K q1q2/r^2

the magnitude of the electric force that a charged particle exerts on another charged particle directly proportional to the product of their charges and inversely proportional to the square of the distance between them

types of materials

insulators

semiconductors

conductors

materials that permit electron from each atom to move freely
through the materials

all electron are bound to the individual atom

have very few electrons

iron

aluminium

plastic

woods

carbon

germanium

silicon

condition of conductor in electrostatic equilibrium

  1. no electric filed inside a conductor
  1. the charges reside on the surface of the conductor

3.the electric field at the surface of a conductor perpendicular to the surface

4.the excess charge on a conductor is more concentrated at regions with high curvature

Gauss law for electrostatics

the net electric flux though any closed surface directly proportional to the enclosed net electric charge

electric flux

rate of electric filed that passes through the plane of a given cross sectional area,A

formula: E.A

Electric Potential

force exerts on a particle,force moves from point A to B,so have the work done

formula:W=Ua-Ub=-(Ub-Ua)

Equipotential surface

a surface where the electric potential at any point on the surface is the same

the electric field is everywere perpendicular to the equipotential surface

the potential on the equipotential surface is everywhere constant