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Physics Paper 1 > magnetic fields > Flashcards

magnetic fields Flashcards

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1
Q

what is a magnetic field?

A

a region where other magnets or magnetic materials experience a force

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2
Q

what is the relationship with the line and magnetic fields?

A

the closer together the lines are, the stronger the magnetic field

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3
Q

where is the magnetic field strongest?

A

at the poles of a magnet

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4
Q

how is a uniform field created?

A

when you place a north and south pole of two bar magnets near each other

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5
Q

what do you need to draw a uniform field?

A

at least three field lines that are parallel to each other and are all the same distance

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6
Q

when not near a magnet why do compasses point to the north?

A

because earth generates its own magnetic field so the core of the earth is magnetic

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7
Q

what are the three main magnetic materials?

A

iron
nickel
cobalt

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8
Q

why is steel magnetic?

A

because it contains iron

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9
Q

what is the magnetic force between a magnet and magnetic material?

A

attractive

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10
Q

what are permanent magnetics?

A

produce their own magnetic field

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11
Q

what are induced magnets?

A

only produce a magnetic field while they are in another magnetic field

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12
Q

why is a force between a magnet and a magnetic material always attractive?

A

because the south pole induces the north pole and vice versa

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13
Q

magnetically soft materials

A

loose their magnetism very quickly

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14
Q

magnetically hard materials

A

lose their magnetism more slowly

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15
Q

uses of magnetic materials

A

fridge doors
cranes
doorbells
speakers

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16
Q

how is a magnetic field created?

A

when a current flows through a long straight conductor

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17
Q

what is the field made up of?

A

concentric circles

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18
Q

what does changing the direction of the current effect?

A

the direction of the magnetic field

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19
Q

what is the right hand thumb rule?

A

point your thumb in the direction of current and curl fingers

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20
Q

what does the right hand thumb rule show?

A

the direction of the field where your finger is pointing

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21
Q

what is the motor effect?

A

a current in a magnetic field experiences a force

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22
Q

How is a force created on a wire?

A

when a current carrying conductor is put between magnetic poles and the fields interact

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23
Q

how does the wire experience the full force?

A

if it is at 90 degrees to the magnetic field

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24
Q

what is flemmings left hand rule used for?

A

find the direction of the force on a current carrying conductor

25
Q

what does your first finger do in the left hand rule?

A

points in the direction of the magnetic field

26
Q

what does your second finger show in the left hand rule?

A

the direction of the current

27
Q

what does your thumb show in the left hand rule?

A

point in the direction of the force

28
Q

how do you find the size of the force?

A

magnetic flux density * current * length

29
Q

what is magnetic flux density?

A

how many field flux lines there are in a region

30
Q

what does magnetic flux density show?

A

strength of the magnetic field

31
Q

when do you use the equation for force size?

A

when the current is at 90 degrees

32
Q

what is a solenoid?

A

a long coil of wire

33
Q

how to increase the strength of a magnetic field produced by a length of wire?

A

wrapping it into a long cool with lots of loops

34
Q

what is the magnetic field like in a solenoid?

A

strong and almost uniform as the lines are pointing in same direction

35
Q

what is the field like outside the solenoid?

A

week apart from at the ends as the lines cancel each other out

36
Q

what does the direction of the field depend on?

A

the direction of the current

37
Q

what is a solenoid an example of?

A

an electromagnet

38
Q

what is an electromagnet?

A

a magnet with a magnetic field that can be turned on and off using an electric current

39
Q

how can you increase the strength of a solenoid?

A

putting a block of iron in the centre of the coil

40
Q

how does iron increase the strength of a solenoid?

A

it acts as an induced magnet

41
Q

what does induce mean?

A

creates

42
Q

what is electromagnetic induction ?

A

the induction of a potential difference in a wire which is experiencing a change in magnetic field

43
Q

what are the two situations where you get an electromagnetic induction?

A

electrical conductor

magnetic field

44
Q

how do you produce an alternating current ?

A

if you keep the magnet moving backwards and forwards or keep it rotating in the same direction

45
Q

how do you reverse current?

A

if you move or rotate the magnet in the opposite direction

46
Q

how do you get an induced potential difference?

A

when a magnetic field through an electrical conductor changes

47
Q

How do you increase the size of the induced potential difference?

A

increase the strength of field
increase speed of movement
having more turns per unit length of coil

48
Q

what happens when a current is induced?

A

produced its own magnetic field that acts against the change trying to return things to what they were

49
Q

what do transformers do?

A

use induction to change the size of the potential difference of an alternating current

50
Q

what happens when an alternating p.d is applied across a primary coil?

A

it produces an alternating magnetic field

51
Q

what happens to the magnetisation in the core in the primary coil?

A

it also alternates as easily magnetised

52
Q

what is the result of the primary coil alternating?

A

the magnetic field inducing potential difference in a secondary coil changes

53
Q

step up transformers

A

step up the potential difference as have more turns on secondary coil then primary

54
Q

step down transformers

A

step down the potential difference as have more turns on primary coil then secondary

55
Q

what can you assume about the input and output power?

A

that they will be equal

56
Q

what do transformers in the national grid produce?

A

high potential difference and low current

57
Q

how can you make the national grid more efficient?

A

higher voltage
low resistance cables
transformers are used

58
Q

how are step down transformers used in the national grid?

A

bring down the p.d to safe usable levels for consumers

Physics Paper 1 (2 decks)

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