Coulomb's Law and Electric Field - ch 21-22

Superconductors:

• materials that are perfect conductors, allowing charge to move without ANY hinderance

• induced charge

• some of its positive and negative charge have been separated due to the presence of a nearby charge

• 

• Couloumb’s Law of Electrostatic:

• particles with the same sign of electrical charge repel each other and particles with opposite signs attract each other

  • equation: F = k ((q1/q2) /r²) r

E0 (permittivity constant) = 8.85 × 10^-12 C² /N * m²

• Shell Theory 1

• a charged particle outside a shell with charge uniformly distributed on its surface is attracted or repelled as if the shell’s charge were concentrated as a particle at its center

• Shell Theory 2:

• a charged particule inside a shell with charge uniformly distributed on its surface has no net force acting on it due to the shell

• elementary charge

• = 1.602 × 10^-19

• quantized

• when a physical quantity such as charge can have only discrete values rather than any values

• annihilation process

• if two charged particles undergo an annihilation process, they have opposite signs of charge

  • annihilation process: electron + positron e → 2 gamma rays

pair production

gamma ray → electron and positron

• if two charged particles appear as a result of a pair production process, they have opposite signs of charge

electric field

• force / positive charge q0

electric field line

helps us visualze the direction and magnitude of electric fields

• closer field lines = stronger field

• originate on positive charge and terminate on negative charge

magnitude of electric field

electric dipole

2 particles with charges of equal magnitude q but opposite signs separated by distance d

lectric dipole moment p

magnitude qd

points from negative charge to positive charge

mangitude of the electric field set up by an electric dipole at a distant point on the dipole axis

z: distance between the point and the center of the dipole

electric field of an extended object

• electric field set up by particle does not apply to an extended object with charge

• how to find it:

electric field due to a charged disk

o = surface charge density

z =distance along the axis from the center of the disk

R = radius of the disk

f particle with charge q is placed in an ecternal electric field E, electricstatic force =

q: if +: force vector goes in same direction as field vecotr

if -, goes in opposite direction

torque on an electric dipole

p = dipole moment

e = external electric field

potential energy U

work done by electric field

potential energy is ____ when electric dipole of dipole moment is _____ to electric field

zero, perpendicular

potential energy is greatest when

p is opposite e

if source charge is positive

e vector points away

if source charge is negative

e vector points towards

E in terms of src and test charge

e = 1/4piE0 x q / r² (direction)