3.7 Gravitational and Electric Fields

Question 1

gravitational field strength

Answer 1

force per unit mass on small object in gravitational field

Question 2

electrical field strenth

Answer 2

force per unit charge on a small positively charged object at that point in the field

Question 3

electric potential

Answer 3

work done per unit charge on a small positively charged object to move it from infinity to that point in the field - potential at infinity is 0

Question 4

equipotential

Answer 4

line or surface in a field along which the electric or gravitational potential is constant

Question 5

escape velocity

Answer 5

minimum velocity an object must be given to escape from the planet when projected vertically from the surface

Question 6

geostationary satellite

Answer 6

• stays above same point on Earth’s equatior -orbits in the same plane as the equator - sametime period of earth’s rotation - orbits in same direction as Earth’s rotation - large orbital radius

Question 7

gravitational field

Answer 7

region surrounding an object in which it exerts a gravitational force on another object

Question 8

gravitational force

Answer 8

attractive force that acts equally on any two objects due to their masses

Question 9

gravitational potential

Answer 9

at a point in a gravitational field is the work done per unit mass to move a small object from infinity to that point in the field

Question 10

gravitational potential energy

Answer 10

• The energy of an object due to its position in a gravitational field.
• The position for 0 GPE is at infinity (sonce the object is so far grav. force experienced is negligible)

Question 11

Newton’s Law of Gravitation

Answer 11

force is proportional to the product of their masses and inversely proportional to the square of the distance between their centres of mass

Question 12

Kepler’s 3rd Law

Answer 12

for any planet the cube of its main radius of orbit is directly proportional to the square of its time period

Question 13

electric field line

Answer 13

direction of a free positive charge in an electric field

Question 14

gravitational field line

Answer 14

of a single mass point towards the centre of the mass

Question 15

potential gradient

Answer 15

point in a field is the potential per unit change of distance along the field line at that point = -field strength at any point

Question 16

radial field

Answer 16

field from which the field lines are straight and converge or diverge from a single point

Question 17

uniform field

Answer 17

region where the field strength is the same in magnitude and direction at every point in the field

Question 18

Coulomb’s Law

Answer 18

force between 2 point charges is proportional to the product of the 2 charges and inversely proportional to the distance between squared

Question 19

gold leaf electroscope

Answer 19

device used to detect charge

Question 20

permittivity of free space

Answer 20

the charge per unit area in coulombs per square metre on oppositely charged parallel plates in a vacuum when the field strength between the plates is 1 Vm^-1