Electric and Gravitational Fields
Force Fields
An area where and object experiences a non contact force
Gravitational Fields
Newtons Law of gravitation
The force between two mases is directly proportional to the product of the mases and is inversely proportional to the separation squared 
Gravitational Field Strength
Force per unit mass exerted by a gravitational field
Gravitational Potential
Work done per unit mass when moving an object from infinity to that point
Equipotentials
Lines with a gravitational field where the GP is constant
Orbits and Satellites :
Kepler's Law... The square of the orbital period is directly proportional to the cube of the radius
Total energy = KE + PE
Escape Velocity
Minimum velocity it must travel at in order to escape the GF
Synchronous Orbit -> Returns to the same point in the sky each day
Geostationary Orbit -> Directly in the same place above the equator
Low Orbit -> Faster than 24hrs, weather systems
Electrical Fields
Columbus Law
The force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance
Electrical Field Strength
Force per unit charge experienced by an object in an electrical field.
Capacitance
Capacitance is the charge stored by a capacitor per unit voltage
Dielectrics
Polara molecules are molecules which have a positive and a negative end. When an electric field is present they will align themselves with the field
Where:
εr = Relative permittivity
ε = permittivity
ε0 = permittivity of free space
Energy stored by a capacitor is given by the area under a graph
Charging a Capacitor
When plotting current against time
When plotting voltage against time
When plotting charge against
Discharging a Capacitor
When plotting current against time
When plotting voltage against time
When plotting charge against time
Time constant = 0.37 of its inital
Time constant = 0.63 of its intial
Magnetic Fields
Magnetic Flux Density (B) is a measure of the strength of the field (Tesla)
The field lines will always point from N > S
Moving Charges within a Magnetic field
A force act on a charged particle when moving through a magnetic field
Cyclotrons
Two dees, Hooked up to AC, this causes the particle to accelerate as it follows . Magnetic field passes through both of the Dees. This causes the particle to take a circular path.
Flux Linkage
The density of magnetic field lines passing through a certain area
Electric Field Strength -> The force per unit charge a positive test charge experiences at that point