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P3 - Physics > Using Magnetic Fields > Flashcards

Using Magnetic Fields Flashcards

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1
Q

Why is insulated wire used to make coils?

A

To prevent a short circuit through the turns of wire

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2
Q

Why is the core made of iron?

A

It is easily magnetised and demagnetised

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3
Q

Why are step down transformers used?

A

Reduces the voltage of the domestic supply

As a higher voltage would be difficult to insulate and would cause electric shock

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4
Q

Explain the advantages of having a national grid system?

A

If the local power station breaks down electricity can still be provided
Electricity can be switched from elsewhere

Power avalible in rural areas
In total fewer power stations needed

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5
Q

Explain simply how a voltage is induced in a coil?

A

Magnetic field lines cut the coil

Potential different countries induced across th coil

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6
Q

How can you tell something is a step down transformer?

A

There are more coils on the input than the output

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7
Q

Explain how a transformer works?

A

There is an alternating current in the primary coil
This produces a magnetic field
The magnetic field lines cut the secondary coil
This induces an alternating voltage across the secondary coil
Hence an alternating current in the secondary coil

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8
Q

What is current?

A

The rate at which electric charge flows past a point in a circuit

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9
Q

What is voltage?

A

The electrical force that would drive an electric current between two points

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10
Q

When there is an alternating current in the primary coil what is produced in the core?

A

A magnetic field

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11
Q

How can you increase the potential difference?

A

More powerful magnet
Coils with more turns
Coil with bigger area

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12
Q

Explain how an alternating input produced an alternating output?

A

Produced a magnetic field
Which is alternating
And induces an alternating voltage across the secondary coil

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13
Q

Why are wires insulated?

A

So the current does not flow through the iron or core

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14
Q

What does an electromagnetic consist of?

A

An insulated wire wrapped around an iron core

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15
Q

How does the size of a force increase?

A

The current increased
The strength of the magnet increased
Number of turns on a coil

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16
Q

How do you reverse the force in the motor effect?

A

If the direction of the current or magnetic field is reversed

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17
Q

What do we mean by electromagnetic induction?

A

The process of creating a potential difference using a magnetic field

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18
Q

How does a magnetic field increase the voltage?

A

A magnetic field can accelerate electrons thus making voltage greater

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19
Q

Why does a coil spin?

A

A force acts on each side in motor effect

The forces are in opposite directions

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20
Q

What system uses pressure in a fluid?

A

Hydraulic systems use pressure in a fluid to exert force

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21
Q

What is a hydraulic system?

A

Any system that transfers force through a liquid

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22
Q

Pressure in a liquid is…?

A

Constant

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23
Q

How can Cs increase the magnetic field?

A

Having more Coils of wire
Having more Current flow through the wire
Having an iron Core

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24
Q

How are electromagnets used in life?

A

For cranes in scrap metal yards for lifting iron and steel

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25
Q

If the wire is parallel to a magnetic field what happens?

A

It dosent experience force

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26
Q

Example of electric motors?

A

Washing machines
Electric cars
Hair dryers
CD players

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27
Q

What direction do magnetic field lines always go in?

A

North to South

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28
Q

How can you change the speed of an electric motor?

A

Alternate the current

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29
Q

How can you reverse the speed in an electric motor?

A

Reverse the current

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30
Q

In an alternating current describe the movement of the wire?

A

Up and down
Or
Vibrates

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31
Q

Why does an alternating current move up and down?

A

Force continually changes direction

Due to the alternating current in the wire

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32
Q

Are magnetic fields made or induced?

A

MADE

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33
Q

In the output what word should be used?

A

Voltage

34
Q

When current flows through a wire what is created?

A

A magnetic field

35
Q

How can you make gauge more sensitive?

A

More coils
Stronger magnet
Larger surface area

36
Q

What is produced in the secondary coil

A

Alternating magnetic field

37
Q

How is an electric current created?

A

Magnet moves in and out of coil
Magnetic field cuts through the coil
Potential difference induced
Electric current induced

38
Q

How can you increase the potential difference?

A

More powerful magnet
Smaller gap between coil and magnet
Coil with more turns
Coil with bigger area

39
Q

What happens when a current flows through a wire?

A

A magnetic field is produced around the wire

40
Q

What is the resultant force in a circular motion?

A

Centripetal force

41
Q

When will the conductor not experience force in the motor effect?

A

If it is parallel to the magnetic field

42
Q

What are electromagnets used for?

A

Cranes lifting iron or steel

43
Q

What frequencies will switch mode transformers operate at?

A

Between 50 kHz and 200 kHz

44
Q

Uses of electromagnets?

A

The scrapyard crane - steel in vehicle sticks to electromagnet when current passes through coil
The circuit breaker - when too much current flows through electromagnet pulls it open and the switch stays open
The electric bell -
The relay - when current passes through the armature is pulled on to electromagnet, which turns a pivot and closes a switch gap

45
Q

Describe an electromagnet?

A

Made of insulated wire wrapped round an iron bar
Current passed along a wire
Magnetic field created around the wire
It is strongly magnetised

46
Q

Why is steel unsuitable for an electromagnet?

A

Because steel keeps its magnetism when the current is switched off

47
Q

What effect is an electric motor designed to use?

A

Motor effect

48
Q

How can you control the speed of an electric motor?

A

Change current

49
Q

How can you reverse the direction of the motor?

A

Reversing the current

50
Q

Describe the direction of force in a wire?

A

Always at right angles to the wire and the field lines

51
Q

How does a diaphragm vibrate?

A

Every time the current changes direction the force reverses direction
The coil is repeatedly forced backwards and forwards
This motion makes the diaphragm vibrate so sound waves are created

52
Q

What is the motor effect?

A

When a current is passed along a wire in a magnetic field
And the wire is not parallel to the lines of the magnetic field
A force is exerted on the wire by the magnetic field

53
Q

When is a potential difference created in a wire?

A

Induced across the ends of the wire when it cuts across the magnetic field lines

54
Q

How does a generator work?

A

Contains coils of wire that spin in a magnetic field
A voltage is induce a crossed the ends of the wire
When it cuts across the magnetic field lines

Electromagnetic induction

55
Q

What volts are mains electricity?

A

230 volts

56
Q

Describe the process of getting electricity as you plug in an appliance?

A

The electricity to run it comes from a power station
The electricity arrives via a network of cables (national grid)
Transformer is used to change the size of the alternating potential difference

57
Q

What does a step up transformer do?

A

Makes the potential difference across the secondary coil less than the potential difference across the primary coil
The secondary coil has more turns than its primary coil

58
Q

What does a step down transformer do?

A

Makes the potential difference across the secondary coil less than the potential differenc across the primary coil
Secondary coil has fewer turns than its primary coil

59
Q

Why is an alternation potential difference across the secondary coil when an alternating current passes through the primary coil?

A

Alternating current passing through the primary coil produces an alternating magnetic field
Lines of the alternating magnetic field pass through the secondary coil
Magnetic field is changing
Creating an alternating pd across the terminals of the secondary coil
Causing an alternating current in the secondary coil

60
Q

Advantages of switch mode transformers?

A

Lighter and smaller than a traditional transformer

Used very little power when there is no device connected across its output terminals

61
Q

What is the core of a switch mode transit meet?

A

A ferrite core oi

62
Q

Why is a core layered (laminated)?

A

To cut out the induced currents in the iron layers

If it were not laminated, the efficiency of the transformer would be greatly reduced

63
Q

What does an MR scan do?

A

See exactly where the swelling is located
Using radio waves
Unlike radio waves they are non ionising

64
Q

When do we use an X Ray or ct scan?

A

To see if there are other affected areas in the neck or chest
The operators or radiographer a must wear film badges to monitor and record their exposure to ionising radiation

65
Q

What happens when a permanent magnetic field is interacted with an alternating magnetic field?

A

Force is produced

66
Q

What provides the centripetal force needed to keep a sati elite in orbit?

A

Gravitational pull of earth

67
Q

Why might a sound inside be louder than outside?

A

Sound reflect off the walls

68
Q

Why not make a core of aluminium?

A

Can’t be magnetised

69
Q

What word describes a planted a orbit?

A

Epithelial

70
Q

What materials is the transformer made from?

A

Iron core

Laminated (to cut out induced currents in layers)

71
Q

Why is the coil laminated?

A

To cut out induced currents in the layers

72
Q

Why use a switch mode transformer?

A

Lighter smaller

Very little power used

73
Q

What frequencies do switch mode transformers operate at?

A

50,000 Hz and 200,000 Hz

74
Q

How does a loud speaker work?

A

A current passes through coil created magnetic field
Magnetic field interacts with permenant magnetic field
Produces a resultant force which caused the cone to move
When current changes force changes to the opposite direction

75
Q

What is an MR scan?

A

Used radio waves to see where a problem area is

76
Q

What are the coils made from?

A

Copper

77
Q

What are the coils covered in?

A

Insulation

78
Q

Where are switch mode transformers used?

A

Mobile phones

79
Q

Why is the wire insulated?

A

To prevent short circuiting

80
Q

Why will voltage produce an electric current?

A

It is part of a complete circuit

81
Q

Why are the wires in coils insulated?

A

To prevent short circuiting

So the current dosent flow through the core

82
Q

Why are the wires in coils insulated?

A

To prevent short circuiting

So the current dosent flow through the core

P3 - Physics (4 decks)

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