Brainscape's Knowledge GenomeTM

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


See full index

Physics A Level > 7 Electric and Magnetic Fields > Flashcards

7 Electric and Magnetic Fields Flashcards

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

Electric field

A

A region in which a charged object will experience a force

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

In which direction do electric fields exert a force?

A

Positive to negative

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

Radial field

A

A field which forms around a point charge

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

Uniform field

A

A field typically formed between two plates

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

What happens to field strength in a radial field?

A

As you go further from the centre the field becomes weaker because the field lines become more spread out

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

Field strength in a uniform field

A

The same throughout because the lines are equally spaced

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

How is electric field strength shown in a drawing

A

The closer the field lines are the stronger the field is at that point

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

Equation linking electric field strength, force on a positive charge and the charge

A

E = F/Q

Electric field strength = force acting on the charge/ charge

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

Equation to work out electric field strength between two plates

A

E = V/d

Electric field strength = voltage between two plates/ distance between plates

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

Lines of equipotential

A

Lines joining points of equal electric potential in an electric field

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

Equation for work done in moving an object of charge between two lines of equipotential (learn)

A

W= Qx (change in)V

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

Uses of electrostatics

A
  • microwaves
  • precipitators in chimneys
  • crop spraying
  • spray painting
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Equation for electric field strength in a radial field

A

E = Qx 8.99x10^9/r^2

Electric field strength = charge of point/ permittivity of free space x 4pi x radius squared

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

Equation for force between two charges in a radial field

A

F = Q1 x Q2 x 8.99x10^9/r^2

Force between charges = charge of point1 x charge of point2 / permittivity of free space x 4pi x radius squared

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

Electric potential

A

The work done per unit charge when a particle is moved in a field

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

Equation for electric potential in a uniform field

A

V =Ed

Electric potential = electric field strength x distance

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

Equation for electric potential in radial field

A

V = Q x 8.99x10^9/r

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

Differences between G fields and E fields

A

•gravitational forces affect all particles with a mass, electrostatic forces only
affect particles carrying a charge
•gravitational forces are always attractive but electrostatic can attract or repel
•it isn’t possible to shield a mass from a gravitational field but this can be done in an electric field

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

What happens when you apply a p.d. to the terminals of a capacitor?

A

The plates become charged and an electric field is created between the plates

20
Q

Equation linking capacitance, charge and voltage

A

C =Q/V

21
Q

What does the area under a voltage against charge graph represent

A

Energy transferred

22
Q

Equation linking work done, voltage and charge in a capacitor

A

W =1/2 Vmax x Q
or
W=Vaverage x Q

23
Q

Equation linking work done, capacitance and voltage

A

W = 1/2 C x V^2

W= 1/2 Q^2/C

24
Q

Uses for capacitors

A
  • camera flash
  • keys on a laptop
  • inside the cable from a satellite dish to a TV
25
Q

How do capacitors charge and discharge?

A

Exponentially

26
Q

Equation linking I, Q, R and C in a discharging capacitor (learn)

A

I= Q/RC

RC = time constant

27
Q

What gives the half life of a discharging capacitor?

A

RC x ln(2)

Time constant x ln(2)

28
Q

Equation linking starting value of charge, voltage or current and and the value at any point when discharging

A

Q = Qo x e^(-t/RC)

V = Vo x e^(-t/RC)

I = Io x e^(-t/RC)

29
Q

When a capacitor discharges for 1 time constant what value of the original charge, voltage or current is given?

A

37% of the original value

Q= 0.37Qo

V= 0.37Vo

I= 0.37Io

30
Q

Magnetic field

A

A region in which a magnetic force will be experienced by a magnetic material

31
Q

In which direction do magnetic field lines travel?

A

North to south

32
Q

What force is felt at neutral points in a field?

A

Nothing since the forces cancel out

33
Q

If current is travelling into the page which way is the magnetic field acting?

A

Clockwise

34
Q

Equation linking force in current carrying wire, magnetic flux density, current in a wire, length of wire, angle between the field and wire

A

F = BILsin(x)

35
Q

Equation linking force on a charged particle, magnetic flux density, charge of particle and velocity of particle

A

F = BQVsin(x)

F= force on charged particle 
B= magnetic flux density 
Q= charge of particle
V= velocity of particle
X= angle between magnetic field and movement of particle
36
Q

Equation to work out magnetic flux density (learn)

A

B = I/A

B= magnetic flux density
I= magnetic flux 
A= area of surface perpendicular to field
37
Q

Equation for flux linkage (learn)

A

Flux linkage = N x I

Flux linkage = number of turns of coil x magnetic flux

38
Q

Electromagnetic induction

A

The generation of a current in a conductor by the interaction of a changing magnetic field with the conductor

39
Q

How can the magnitude of an induced electromagnetic voltage be increased

A
  • stronger magnet
  • moving the magnet faster
  • increasing the turns if the coil
40
Q

What happens when a magnet falls through a coil

A
  • a current is induced in the coil
  • the coil opposes the movement of the magnet due to Lenz’s law
  • as the magnet falls out the other end of the coil the “poles” of the coil flip in order to oppose the direction of the magnet
  • this causes the current to change direction
41
Q

Faraday and Lenz’s law

A

E= -d(NI)/dt

E= -d(NBA)/dt

emf= - change in number of coils x magnetic flux/ change in time

42
Q

Uses of electromagnetic induction

A
  • large rotating coils generating electricity
  • step up or step down transformers
  • charging phones
  • braking on trains
  • braking on electric cars
43
Q

Transformers

A

Transformers increase or decrease the voltage of alternating current electrical power supplies

44
Q

How do transformers work?

A
  • primary coil produces changing magnetic flux
  • this magnetic flux is linked to the secondary coil by iron core
  • therefore the magnetic flux linkage in the secondary coil varies continuously
  • the change of this flux linkage induces a varying emf in the secondary coil
45
Q

Transformer equation (learn)

A

Vsecondary/ Vprimary= Nsecondary/ Nprimary

46
Q

Equation to work out average voltage from peak voltage

A

Vrms = Vo/ route 2

Irms = Io/ route 2

47
Q

If three identical magnets are dropped through a cylinder of cardboard, copper and plastic, which will hit the floor first and why?

A

Cardboard and plastic first then copper

The copper opposes the direction of motion of the magnet so slows it down

Physics A Level (11 decks)

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