electric fields Flashcards
what is electrostatics
study of electricity at rest (static)
what does it mean when an object is neutral
contain positive and negative charges, but in equal numbers
when is an object electrically charged
when there is a little bit more of one type of charge than the other on the object
since protons dont move,how do charges become pos/neg
positive charges result from shortage of electrons;negative charges result from excess of electrons
what is charge measured in
coulombs C
physical quanity q
proton
p+
positively charged sub atomic particle
1.6 X 10^-19 C
heavy
found in nucleus - DONT MOVE
how are electrons transfered
through friction
atom
the smallest particle of a chemical element that can exist.
insulators
materials that do not allow electrons to move through them because the electrons are bound to the atoms within the material
conductors
Materials that allow charges (electrons) to move relatively freely through them. due to their structure of positive metal cations which are fixed in position and surrounded by a sea of delocalised electrons.
polarisation
attraction between uncharged (neutral) and charged objects
how does an electrostatic force come about
2 charges interacting
what does the size/intensity of force depend on
size of charge (bigger the charge,greater the force)
distance between charges (smaller the distance,greater the charge)
polar molecules
molecules that have already been polarised( have a more positive/negative side
STILL NEUTRAL
how does polarisation work (4)
charged object exert a force on neutral object
can attract bound electrons to move
molecules in neutral object shift
resulting in more pos/neg side (OBJECT IS STILL NEUTRAL)
what does the principle of conservation of charge imply
if charged body in closed system has shortage of electrons, there must be another body/bodies in that system with excess of electrons
net charge of system formula
Qnet = Q1 + Q2
what happens when 2 charged bodies (identical in size,insulated) are brought into contact
state the formula
movement of electrons between bodies, after separation they will carry same charge
Qnew=Q1 + Q2 / 2
Coulombs Law
Two point charges in free space or air exert forces on each other. The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between the charges
don’t include signs in calculations
coulombs law eq
F = kq1q2/ r^2
F= force between charges (Newton-N)
q1q2 = charges (Coulombs - C) (no neg signs)
k= Coulombs constant (9 X 10^9)
r = distance between charges (metres m)
Quantisation of charge
formula
Q = nqe
Q= charge (C)
n= number of electrons
qe= charge on 1 electron (1.6 X 10^-19 C - constant)
qe/charge of 1 electron
1.6 X 10^-19
Coulombs constant
k
9 X 10^9
describe the relationships within coulombs law
force between 2 charges is directly proportional to product of charges
force between 2 charges is inversely proportional to the square of distance between charges
