Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Fields > Flashcards

Fields Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

Direction of the field

A

Gravitational- direction of the force on a small test mass at that point

Electric- direction of a force on a positive charge at that point

Magnetic- direction of force in a magnetic North Pole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Radial field

A

Directed towards centre
Diverges
Strength of field decreases as density of lines decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Uniform field

A

Lines are equally spaced and parallel
Same magnitude and direction throughout
Near field limit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Newton’s law of gravitation

A

F= GMm/ r^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Gravitational constant

A

6.67 x 10^-11 Nm^2kg^-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Relationship T and r

Kepler’s law

A

T^2 proportional to r^3

T^2 = 4pi^2/ GM r^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

As r increases …

A

Speed of satellite decreases (v = GM/r)

Period of satellite increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Geosynchronous orbit

A

Period of 24 hours
Or it’s above the equator
Or it’s in the same direction as the Earth’s rotation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Geosynchronous satellites in communication

A

Dish can be pointed at a fixed point (does not have to track)

Dishes needed as the weak signal can be collected across the area of the disc and focussed on the receiving antenna

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Gravitational field strength

A

g = GM/r^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Gravitational potential

A

V =-GM/r

Scalar

Units = J/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

V at infinity

A

0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Work (gravitational)

A

W = mdV

Away = positive
Towards =negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Gravitational potential energy

A

U= -GMm/r

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Kinetic energy

A

Ek= GMm/2r

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Total energy (gravitational)

A

Et = -GMm/2r

Negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Increasing Et

A

Gains energy, less negative, r increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Escape velocity

A

Root (2gR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Coulomb’s law

A

F = Qq/4pi epsilon r^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Positive

A

Repulsive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Epsilon 0

A

Permittivity of free space
Ease of setting up an electric field
8.85 x10^-12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Similarities between gravitational and electric fields

A

Inverse square law for forces
Non contact forces
Infinite range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Difference gravitational and electric fields

A

Electric acts on changes, gravitational on masses

Gravitational is attractive whereas electric can be attractive or repulsive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Electric field strength

A

E= Q/ 4 pi epsilon r^2

25
Q

Electric potential

A

V = Q/ 4pi epsilon r

Scalar

26
Q

Sign of W

A

+/- negative work

+/+ or -/- positive work

27
Q

Potential gradient (electric)

A

E = dV/ dr

28
Q

Work (electric)

A

W =qdV

29
Q

Equipotential lines

A

Lines of equal potential

At right angles to the field

30
Q

Electrical potential energy

A

U = Qq/4 pi epsilon r

Energy of whole system

31
Q

Distance of closest approach

A

R min = Qq/ 2pi epsilon m v^2

32
Q

Capacitance

A

C=Q/V

Farads F

33
Q

Work done by a capacitor

A

E = 1/2 QV

E = 1/2 C V^2

E = 1/2Q^2/C

34
Q

Time constant

A

RC

Seconds

35
Q

Charging a capacitor

Charge

A

Q = Qmax (1-e^-t/RC)

36
Q

Charging a capacitor

Voltage

A

V = Vmax (1-e^-t/RC)

37
Q

Charging a capacitor

Current

A

I = Imax e^-t/RC

38
Q

Discharging a capacitor

Charge

A

Q = Qo e^-t/RC

39
Q

Discharging a capacitor

Voltage

A

V = Vo e^-t/RC

40
Q

Discharging a capacitor

Current

A

I = Io e^-t/RC

41
Q

Relative permittivity

A

Epsilon r = C/Co

C = capacitance with dielectric 
Co = capacitance with vacuum
42
Q

Capacitance equation (dielectric)

A

C = epsilon o epsilon r A/ d

43
Q

Current at right angles to the field feels force

A

F = BIl

44
Q

Fleming’s left hand rule

A 
Thumb= force 
1st = field 
2nd = current
45
Q

Force on a moving charge perpendicular to the field

A

F = Bqv

46
Q

Charged particle moving parallel to a magnetic field

A

No force

47
Q

Radius of a circular path

A

r= mv/Bq

48
Q

Time period for 1 full circle

A

T = 2 pi m/ Bq

49
Q

Acceleration in a magnetic field

A

Changes direction so changes v so accelerated
Circular path
F is perpendicular to v and B
No work done so Ek does not change, so no increase in speed

50
Q

Why a cyclotron needs to be evacuated

A

Collisions, loss of Ek, deceleration, changes v which changes r

51
Q

Alternating charge of the dees of a cyclotron

A

So proton accelerated across the gap
Needs to alternate and reverse electric field
Polarity can switch at regular intervals
Frequency = Bq/ 2 pi m

52
Q

The feature of the ions that allows them to be separated

A

In ion separator v B and q are constant
r= mv/Bq
Ions departed due to their mass

53
Q

Velocity selected in a velocity separator

A

Only 1 velocity where Bqv= Eq and there will be no deflection

V=E/B

54
Q

Why ions originally have a range of speeds

A

Gases
Random continuous motion of gases
Brownian motion
Move with varying speeds and directions

55
Q

Magnetic flux

A

Phi= BA cos theta

Theta= angle between field lines and normal to plane of the area

56
Q

How to reduce magnetic flux

A

Reduce B
Reduce A
Rotate- as the angle changes as will the area perpendicular to the field

57
Q

Faraday’s law induced EMF

A

EMF = N dphi/ dt

58
Q

To increase the induced EMF

A

Increase N
Increase v and increase l (which increases A)
Increase B

59
Q

For a rod length l moving at constant speed v

A

EMF = BvL

Physics (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions