Fields and their Consequences Flashcards
(20 cards)
gravitational field definition
a force field is a region in which a body experiences non-contact forces
newtons law of gravitation
the gravitational force is directly proportional to the product of the masses and inversely proportional to the square of the distance between them
gravitational field strength
the force per unit mass
the value of this at earths surface is 9.81ms-1
gravitational potential
the point at which gravitational potential energy that a unit mass would have
gravitational potential difference
the energy needed to move a unit mass
two points at different distances will have a different gravitational potential
equipotentials
lines and surfaces that join together all of the points within a gravitational potential
as you travel along an equipotential the potential doesn’t change
satellites
kept in orbit by gravitational forces
any smaller mass that orbits a larger mass
escape velocity
the minimum speed required for an unpowered object to leave the gravitational field of a planet and not fall back towards the planet due to gravitational attraction
v= square root of 2GM/r
synchronous orbit
when an orbiting object has the same orbital period as the object it is orbiting
geostationary satellites are examples of this- they are always the same point above earth
low orbiting satellites
180 and 2000km above earth
cheaper snd require less powerful transmitters
difference between gravitational and electric fields
gravitational- between 2 masses and only attractive
electric- between 2 charges and can be attractive or repulsive
coulombs law
the force on a charged object in an electric field
the electric force is directly proportional to the product of the masses and inversely proportional to the square of the distance between them
electric field strength
the force per unit positive charge that one C would experience in a positive field
electric potential
all points in an electric field have ana absolute electric potential- this is the absolute electric potential energy that 1C would have at that point
electric potential difference
if two points in an electric field have a different electric potential then there is electric potential difference between them
capacitance
the capacitance of an object is the amount of charge is is able to store per unit of potential difference across it
what is a capacitor
an electrical component that can store electrical charge
2 conducting plates that are separated by an electrical insulator - dieletric
permittivity
a measure off how difficult it is to generate an electric field in a medium.
the higher the permittivity, the more charge is needed to generate an electric field
charging and discharging a capacitor
when connected to a power supply, current flows in the circuit- charging the capacitor
the electrons flow from the negative terminal on to the plate and build up charge
to discharge, take out the battery and reconnect the circuit
time constant and half life
when the discharge time is equal to RC the equation becomes
Q/Q0 = 1/e where e is 0.37
