Fields and their Consequences

Question 1

gravitational field definition

Answer 1

a force field is a region in which a body experiences non-contact forces

Question 2

newtons law of gravitation

Answer 2

the gravitational force is directly proportional to the product of the masses and inversely proportional to the square of the distance between them

Question 3

gravitational field strength

Answer 3

the force per unit mass

the value of this at earths surface is 9.81ms-1

Question 4

gravitational potential

Answer 4

the point at which gravitational potential energy that a unit mass would have

Question 5

gravitational potential difference

Answer 5

the energy needed to move a unit mass

two points at different distances will have a different gravitational potential

Question 6

equipotentials

Answer 6

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

Question 7

satellites

Answer 7

kept in orbit by gravitational forces

any smaller mass that orbits a larger mass

Question 8

escape velocity

Answer 8

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

Question 9

synchronous orbit

Answer 9

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

Question 10

low orbiting satellites

Answer 10

180 and 2000km above earth

cheaper snd require less powerful transmitters

Question 11

difference between gravitational and electric fields

Answer 11

gravitational- between 2 masses and only attractive

electric- between 2 charges and can be attractive or repulsive

Question 12

coulombs law

Answer 12

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

Question 13

electric field strength

Answer 13

the force per unit positive charge that one C would experience in a positive field

Question 14

electric potential

Answer 14

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

Question 15

electric potential difference

Answer 15

if two points in an electric field have a different electric potential then there is electric potential difference between them

Question 16

capacitance

Answer 16

the capacitance of an object is the amount of charge is is able to store per unit of potential difference across it

Question 17

what is a capacitor

Answer 17

an electrical component that can store electrical charge

2 conducting plates that are separated by an electrical insulator - dieletric

Question 18

permittivity

Answer 18

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

Question 19

charging and discharging a capacitor

Answer 19

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

Question 20

time constant and half life

Answer 20

when the discharge time is equal to RC the equation becomes

Q/Q0 = 1/e where e is 0.37