define electric field
Region of field where charged particles experience a force
the electric field is always directed
- away from positive charge
- towards negative charge
define electric field strength NC^-1
the force per unit positive charge experienced by a small stationary test charge placed at that point
what is the equation for electric field strength E in respect to F
E = F / q
F=force
q=charge
unit: Vm^-1 or FC^-1
what are the properties of uniform electric field (need to know how to draw this)
- field lines are always from positive to negative
- electric field lines are equally spaced
- electric field strength is constant at all points in the field
what are the properties of radial electric field (need to know how to draw this)
- field line exit the surface of charge and increase distance as it is further away
- electric field strength decrease as it is further from the charge
- the closer the field lines the stronger the field strength
formula for electric field strength of uniform electric field btw 2 charged plates
E = ∆V/∆d
E= field strength; NC^-1
V=p.d. btw the plates; v
d=distance btw the plates; m
how is E = ∆V/∆d derived
W = Fd. &. W=qV
=> Fd = qV
=> F/q = V/d =E
if one of the parallel plate is earthed then its p.d. is
0 volts
hows the motion of point charge move through an uniform electric field
- go through a parabolic trajectory
- positive point charge to negative plate, vice versa
what effects the motion of point charge through an uniform electric field
- the bigger mass of point charge less deflection
- the smaller the charge, less deflection
- higher the speed, less deflection
- remember that less deflection means the charge moves a larger distance and the curve has a smaller angle
define Coulomb’s Law
the force btw 2 point charges is directly proportional to the product of their charges but inversely proportional the square of their separation
equation for Coulomb’s’ law
F = (Q1Q2 )/ (4π * ε0 * r^2) = (Q1Q2 )*k/ (r^2)
what is k (electric field), given in exam
k is coulomb’s constant = 1/(4π*ε0)
ε0 is permittivity of free space
what type of force btw charges
electrostatic force
need to draw diagrams btw
1. parallel plates of uniform electric field
2. oppositely charged point masses
3. same charge point masses
4. point mass and plates
look up in notes
coulomb’s law is for
radial electric field/ point masses/ outside of an uniform spherical charge
can’t be used for irregular shaped objects
electric force and field strength are scalar or vector
both vector quantities => can be added like any other vectors
equation of E of point charge
E = Q / (4π ε0r^2)
define electric potential
the work done per unit positive charge to bring a small test charge form infinity to that point, volts
equation for electric potential, V
V = Q/ (4π * ε0 * r) = E * r
equation of electric potential energy Ep
Ep = (Q*q)/ (4π * ε0 * r); J
why is there positive and negative for V (electric)
scalar quantity
positive at positive charge
negative at negative charge
define electric potential gradient
the rate of change of electric potential with respect to the displacement in the direction of the field
