Chapter 22 Electric Fields Flashcards
what are electric fields due to?
Due to charges
what can you model a charged sphere as?
As a point charge at its centre.
which direction do electric fields go?
+ to -
what is electric field strength? Therefore the equation? Unit?
Force experienced per unit POSITIVE charge at that point.
(Vector quantity)
E = F/Q
NC-1
describe Electric Field lines
- equally spaced and parallel
- arrows point to direction of field
- closer lines = greater field strength
state Coulomb’s Law
any 2 point charges exert an electrostatic force between them that is directly proportional to product of their charges and inversely proportional to the square of the distances
F (d.p) Qq
F (d.p) 1/r^2
combine E = F/Q and F = Qq/4piEr^2
Electric field strength = Q/4piEr^2
G.Field vs E.Field
property that creates the field?
G.field - mass
E.field - charge
G.Field vs E.Field
Type of field produced?
G - always attractive (direction always towards object)
E -
[+ charge ]
outwards, repulsive field, repels positive charge.
[- charge]
inwards, attractive field, attracts positive charge .
G.Field vs E.Field
field strength?
G - g = F/m
E - E = F/q
G.Field vs E.Field
Forces between particles?
G - F & Mm , F & 1/r^2
E - F & Qq , F & 1/r^2
G.Field vs E.Field
Forces and field strength equations
G - F = -GMm/r^2 , g = -GM/r^2
E - F = Qq/4piEr^2 , E = Q/4piEr^2
G.Field vs E.Field
shape of field around a field
G - point MASS produces radial field
E - point CHARGE produces radial field
what is a uniform electric field?
A field produced between two parallel oppositely charged plates.
The field is constant
Equation for the work done
Work done = force x distance in direction of force
what is done when moving a charge in an electric field?
Work is done
define the potential difference
and
state the equation
The work done per unit charge in moving a charge from one point to another in a field.
V = W/Q
define electric potential
work done per unit charge to bring a positive charge from infinity to that point.
derive W = EQd
Work done = V x Q = F x D
so = EqD
what is electric potential at infinity?
0
state equation for electric field strength for parallel plates
E = V/d
so, V = Ed
why does an electron have constant acceleration?
Constant electrostatic force due to uniform electric fields between the plates - therefore constant acceleration.
what is permittivity
degree to which a medium can resist the flow of electric charge
is motion of particles parallel or perpendicular to the field?
parallel
in uniform E.F, what is gain in Ek = to ?
work done in moving the charge through the distance between the plates.
where:
W = F x d
Describe the particles during horizontal motion
acceleration = 0
time = x/ Vh
Describe the particles during vertical motion
u = 0
(F = ma , a = F/m, F= Eq so)
a= Eq/m
Vv = u + at = Vv = at
= Eq/m x X/Vh
= Eqx/VhM
