Flashcards in Section 6 - Fields Deck (47)

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1

## What is a gravitational field?

### The force field round a mass.

2

## What is a field line (gravitational)?

### The path a smaller mass would follow if pulled towards a larger mass.

3

## Define the strength of a gravitational field (g)

### The force per unit mass on a small test mass placed in the field.

4

## Describe a radial field

### The field lines are like the spokes of a wheel, towards the centre.

5

## What happens to g in a radial field?

### Decreases with increasing distance from the massive body.

6

## Describe a uniform field

### Field lines are parallel and equally spaced.

7

## What happens to g in a uniform field?

### Magnitude and direction of g is constant.

8

## Define gravitational potential energy

### The energy of an object due to its position in a gravitational field.

9

## Define gravitational potential

### Gravitational potential at a point is the work done per unit mass to move a small object from infinity to that point.

10

## What are equipotentials?

### Surfaces of constant potential.

11

## Define potential gradient (gravitational)

### Potential gradient at a point in a gravitational field is the change in potential per metre at that point.

12

## What is Kepler's Third Law?

### For all planets r^3/T^2 is the same.

13

## What are the assumptions in Newton's law of gravitation?

###
Always attractive

Proportional to the mass of each object

Proportional to 1/r^2 (r is distance between objects)

14

## What is the name for G?

### Universal constant of gravitation

15

## Define escape velocity

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

16

## What is the formula to remember for escape veloctiy?

###
v(esc)=sqrt(2gR)

g is gravitational field strength

R is the radius of the planet

17

## What is the height of a geostationary satellite above the Earth?

### 35600km

18

## What do electrical conductors contain a lot of?

### Free electrons

19

## What do electrically insulating materials not contain?

### Free electrons

20

## What is a field line (electric)?

### The path a free positive test charge follows.

21

## Describe a field between two oppositely charged plates

###
Field lines run parallel

At right angles to the plates

At the edges of the field the lines are slightly curved

22

## What kind of a field is it between two oppositely charged plates?

### Uniform field

23

## Define electric field strength at a point in the field

### The force per unit charge on a positive test charge placed at that point.

24

## Electric field strength between plates is proportional to what?

###
Q/A

Q - charge

A - surface area

25

## Define electric potential at a point in an electric field

### Work done per unit positive charge on a positive test charge when it is moved from infinity to that point.

26

## Define potential gradient (electric) at a point in an electric field

### The change of potential per unit change of distance in a given direction.

27

## How is potential gradient effected if the field is non-uniform?

###
Varies according to position and direction.

Closer equipotentials means greater potential gradient at right angles to them.

28

## How is potential gradient effected if the field is uniform?

###
Equipotentials between the plates are equally spaced parallel to the plates.

Potential gradient is constant.

29

## Define electric field strength

### The negative of the potential gradient.

30