Brainscape's Knowledge GenomeTM

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


See full index

A Level Physics > Magnetic Fields > Flashcards

Magnetic Fields Flashcards

1
Q

What does a current-carrying conductor produce

A

a magnetic field

When interacting with an external magnetic field, it will experience a force

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

When will a current-carrying conductor experience the maximum magnetic force

A

if the current through it is perpendicular to the direction of the magnetic field lines

It experiences no force if it is parallel to magnetic field lines

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

What is the strength of the magnetic field known as, and what is its unit

A

the magnetic flux density, B

measured in Tesla (T)

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

Describe the components of the force-flux density equation

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

What does the force-flux density equation show

A

the greater the current or the magnetic field strength, the greater the force on the conductor

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

What is Flemings’s left hand rule

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

What are the symbols for a magnetic field which goes into or out of the page

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

Describe how moving charges may curve in direction

A

For example, when a positively charged particle enters a magnetic field into the page from left to right:

-Using Fleming’s left-hand rule, the first finger points into the page and the second finger (current) points to the right
- This means the force is upwards
- The particle is then pulled in the direction of this force (upwards). This means the direction of the current also changes direction slightly (slanting upwards)
- This means the force will also change direction since it still needs to keep perpendicular to the current and the field
- Therefore, the moving charges will follow a circular trajectory

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

Magnetic flux density def

A

The force acting per unit current per unit length on a current-carrying conductor placed perpendicular to the magnetic field

Measured in Tesla

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

unit of a Tesla def

A

A wire carrying a current of 1A normal to a magnetic field of flux density of 1 T with force per unit length of the conductor of 1 N m-1

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

how can a particle experience no magnetic force

A

when it travels parallel to a magnetic field

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

What does the force on a current carrying wire depend on

A
  • Strength of uniform magnetic field
  • Size of current
  • Length of wire in the field
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

For a particle in a magnetic field, travelling in a circular path, what is the centripetal force

A

The magnetic force

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

Draw a diagram of the forces acting on a particle which moves in a circular path

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

What are cyclotrons

A

a type of particle accelerator that accelerates charged particles (eg. protons) from their centre along a spiral path

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

What kind of medical research are cyclotrons used for

A

Producing medical isotopes (tracers)

Creating high-energy beams of radiation for radiotherapy

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

Draw and label a diagram of a cyclotron

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

Describe the process of accelerating a particle in a cyclotron

A
  • A source of charged particles is placed at the centre of the cyclotron and they are fired into one of the electrodes
  • The magnetic field in the electrode makes them follow a semi-circular path, since it is perpendicular to their motion until they eventually leave the electrode
  • The potential difference applied between the electrode accelerates the particles across the gap to the next electrode (since there is an electric field in the gap)
  • Since the speed of the particles is now higher, they will follow a circular path with a larger radius (since r ∝ v) before leaving the electrode again
  • The potential difference is then reversed so the particles accelerate towards the opposite electrode
  • This process is repeated as the particles spiral outwards and eventually have a speed large enough to exit the cyclotron
  • The alternating potential difference is needed to accelerate the particles across the gap between opposite electrodes
  • Otherwise, the particles will only accelerate in one direction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Derive the equation for the radius of the path of a particle travelling in a magnetic field

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

What is electromagnetic induction and give examples

A
  • when an e.m.f is induced in a closed circuit conductor due to it moving through a magnetic field
  • This happens when a conductor cuts through magnetic field lines
  • The amount of e.m.f induced is determined by the magnetic flux

Examples are a flat coil or a solenoid

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

magnetic flux definition

A

The product of the magnetic flux density and the cross-sectional area perpendicular to the direction of the magnetic flux density

(the total magnetic field that passes through a given area)

22
Q

When is magnetic flux at a maximum/minimum

A
  • It is a maximum when the magnetic field lines are perpendicular to the plane of the area
  • It is 0 when the magnetic field lines are parallel to the plane of the area
23
Q

Draw a diagram of maximum magnetic flux and minimum magnetic flux

A
24
Q

What is the unit of magnetic flux

A

Webers (Wb)

25
Q

What do the components of the magnetic flux equation mean

A
26
Q

Magnetic flux linkage def

A

The product of the magnetic flux and the number of turns of the coil

27
Q

What do the components of the magnetic flux linkage equation mean

A
28
Q

What is magnetic flux linkage measured in

A

Weber turns (Wb turns)

29
Q

What is the symbol for magnetic flux linkage

A

ΦN

30
Q

What do the components of the magnetic flux linkage equation mean (When the magnet field lines are not completely perpendicular to the area A)

A
31
Q

When is an emf induced in a circuit

A

When there is:
- A changing magnetic flux density B
- A changing cross-sectional area A
- A change in angle θ

32
Q

What is electromagnetic induction

A

when an e.m.f is induced when a conductor moves through a magnetic field

33
Q

What happens when a conductor cuts through magnetic field lines

A
  • This causes a change in magnetic flux (ΔΦ)
  • Which causes work to be done
  • This work is then transformed into electrical energy
34
Q

Electromagnetic induction def

A

The process in which an e.m.f is induced in a closed circuit due to changes in magnetic flux

35
Q

When may electromagnetic induction occur

A

When:
- A conductor cuts through a magnetic field
- The direction of a magnetic field through a coil changes

36
Q

What is electromagnetic induction used for

A
  • Electrical generators which convert mechanical energy to electrical energy
  • Transformers which are used in electrical power transmission
37
Q

What factors increase an induced e.m.f when a bar magnet is moved through a coil connected to a voltmeter to induce an e.m.f

A
  • Moving the magnet faster through the coil
  • Adding more turns to the coil
  • Increasing the strength of the bar magnet
38
Q

What factors increase an induced e.m.f when a wire is moved between two magnets connected to a voltmeter to induce an e.m.f

A
  • Increasing the length of the wire
  • Moving the wire between the magnets faster
  • Increasing the strength of the magnets
39
Q

What does Faraday’s law state

A

The magnitude of the induced e.m.f is directly proportional to the rate of change in magnetic flux linkage

40
Q

What does Lenz’s law state

A

The direction of the induced emf is such that it will oppose the change of flux producing it

41
Q

Describe the experimental evidence for Lenz’s law

A
42
Q

What do the components of Faraday’s law equation mean

A
43
Q

What does Faraday’s law equation demonstrate

A

that the gradient of a magnetic flux against time graph is the e.m.f

44
Q

What is the equation that combines Faraday and Lenz’s laws AND what does it demonstrate

A
45
Q

Draw a diagram which shows how a straight conducting rod moving through a magnetic field will have an e.m.f induced in it

A
46
Q

Derive the equation for the induced e.m.f in a conductor as it moves through the magnetic field

A
47
Q

When is induced emf at a maximum/ minimum

A
  • Maximum when θ = 90o. The magnetic field lines are parallel to the plane of the area (or the normal to the area is perpendicular to the field lines)
  • 0 when θ = 0o. The magnetic fields lines are perpendicular to the plane of the area (or the normal to the area is parallel to the field lines)
48
Q

Draw a graph of the magnetic flux linkage and e.m.f induced as a coil rotates in a magnetic field

A
49
Q

Describe the derivation and components of the ‘emf induced in a rotating coil’ equation

A
50
Q

Derive the frequency equation

A
51
Q
A
52
Q
A

A Level Physics (33 decks)

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