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physics > Magnetism And Electronganetism > Flashcards

Magnetism And Electronganetism Flashcards

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1
Q

What are the poles of a magnet?

A

Where the magnetic forces are strongest

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2
Q

Where is the magnetic force the strongest?

A

At the poles

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3
Q

What do magnets produce ?

A

Magnetic fields

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4
Q

What are the two poles of a magnet called?

A

North and south

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5
Q

Which way do magnetic field lines go ?

A

North to south

They show which way the force acts

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6
Q

What shows the strength of the magnetic field?

A

The distance away from the magnet the field lines are

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7
Q

When do magnets attract?

A

When the poles are opposite

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8
Q

When do poles repel ?

A

When the poles are the same

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9
Q

What show the direction o the magnetic field?

A

Compasses

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10
Q

What do compasses show

A

The direction of the magnetic field

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11
Q

What type of force is attraction and repulsion for a magnet?

A

Non contact

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12
Q

What is a permanent magnet?

A

Produces its own magnetic field

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13
Q

What type of magnet produces it’s own magnetic field?

A

Permanent

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14
Q

What is and induced magnet?

A

A material that becomes magnetised when places in a magnetic field

Can loose it’s magnetism

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15
Q

What so the region around a magnet where a force acts on another magnet or on a magnetic material ?

A

The magnetic field

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16
Q

What is a magnetic field ?

A

the region around a magnet where a force acts on another magnet or on a magnetic material

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17
Q

Where do compass needles point ?

A

North

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18
Q

What inside a compass?

A

A tiny bar magnet

The North Pole is attracted to the South Pole if any other magnet is near

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19
Q

How do we know that the earth has a magnetic field ?

A

When a magnet is not near

The compass always points north

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20
Q

How can u see the shape of a magnetic field

A
  • compass

- iron fillings

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21
Q

What is a disadvantage of using iron fillings?

A

Don’t show direction

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22
Q

What happens when a current flows through a wire ?

A

A magnetic field is created around the wire

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23
Q

What is the angelic field around a wore made up of ?

A

Concentric circles perpendicular to the wire

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24
Q

How do u work out the direction of a current through a wire ?

A

Right hand thumb rule

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25
Q

What does the strength of the magnetic field around a wire depend on ?

A
  • distance from the wire

- size of the current

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26
Q

What is a solenoid ?

A

A coil of wire

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27
Q

How can u increase the strength of the magnetic field a magnet produces ?

A

Wrapping the wire into a coil

Solenoid

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28
Q

What is the magnetic field inside a solenoid like ?

A

Strong and uniform

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29
Q

How can u increase the strength of a solenoid even more ?

A

Putting a block of iron in the middle

30
Q

What is a solenoid with an iron called ?

A

An electromagnet

31
Q

What happens if u stop the current in a solenoid ?

A

The magnetic field drops

32
Q

Why are electro magnets useful ?

A

They can be turned on and off

33
Q

Where are electromagnets used ?

A
  • picking up magnetic materials
  • within circuits as switches
  • electric bells
  • security doors
34
Q

What is the shape of the field lines around an electromagnet?

A

The same as a bar magnet

35
Q

What does the strength of an electromagnet depend on ?

A
  • number of turns in solenoid

- size if the current

36
Q

What is an electric motor?

A

When a coil of wire carrying a current in a magnetic field rotates

37
Q

What angle do forces act to the magnetic field ?

A

90 degrees

Right angle

38
Q

What is the motor effect ?

A

When a conductor carrying a current is placed in a magnetic field the magnet producing the field and the conductor exert a force on each other

39
Q

What does your thumb represent in the right hand rule ?

A

Current

40
Q

What do your fingers represent in right hand rule

A

Direction of magnetic field

41
Q

What does your thumb represent on Flemings left hand rule ?

A

Force

42
Q

What does your second finger represent on Flemings left hand rule ?

A

Current

43
Q

What does your first finger represent on Flemings left hand rule ?

A

Magnetic field

44
Q

What does the forec acting on a conductor in a magnetic field depend on?

A
  • magnetic flux density
  • size of current
  • length of conductor
45
Q

What is magnetic flux density ?

A

How many field lines there are in a Region

This show strength it the magnetic field

46
Q

What is the equation for magnetic flux density ?

A

Magnetic Force
Flux. =——————————-
Density Current x length of wire

47
Q

What are the units for magnetic flux density ?

A

T

Tesla

48
Q

What are electric motors used for?

A
  • food mixers
  • DVD player
  • hairdryers
49
Q

How do loudspeakers and headphones use to convert variations in a current in electrical circuits to pressure variations in sound waves ?

A

Motor effect

50
Q

What does cutting field lines do ?

A

Induces a potential difference

51
Q

What is the generator effect ?

A

The induction of a potential difference and current if it’s a complete circuit In a wire that is experiencing a change in magnetic field

52
Q

What does Induce mean ?

A

Create

53
Q

How do u create the generator effect

A

Moving a magnet in a coil of wire

Cutting field lines

Moving a conductor in a magnetic field

54
Q

What happens when your move w magnet
Side to side inside a coil of wire .
?

A

Creates a little bip of current if th conductor is part of a complete circuit

55
Q

What Happens if u move the magnet inside a coil of wire in the opposite direction, or the poles are reversed ?

A

Potential difference/current will be reversed

56
Q

What Happens if u move the magnet inside a coil of wire back and forth ?

A

Potential difference keeps swapping direction

Produces an alternating current

57
Q

What do transformers do ?

A

Change the potential difference

Only for alternating current

58
Q

What are transformers made of ?

A

Two coils - primary and secondary

Joined with an iron core

59
Q

What do step up transformers do ?

A

Increase the voltage

From 230v to 132 000v

60
Q

Why is iron used in transformers ?

A

It is easily magnetised

61
Q

What do step down transformers do ?

A

Decrease the voltage to 230 v

So it is safe to use In homes

62
Q

What is the difference between step up transformers and step down transformers ?

A

Step up - increase voltage

            - more turns in secondary coil

Step down - decrease voltage

                  - more turns in primary coil
63
Q

Which transformer has more turns on the primary coil?

A

Step down

64
Q

Which transformer has more turns on the secondary coil?

A

Step up

65
Q

What is the transformer equation ?

A

Input pd. number of turns in primary coil
————. = —————————————
Output pd. number of turns in secondary coil

66
Q

What does transformer being nearly 100% efficient mean ?

A

Input power = output power

67
Q

Describe the magnetic field lines around a current carrying wire ?

A

Concentric circles around the wire

68
Q

Suggest a metal suitable for the core of an electromagnet.

A

Iron

69
Q

What happens if the current in an electromagnet if the current is cut off? And why

A

Anything it was holding will fall because an electromagnet only has magnetism if a current is flowing

70
Q

How is the direction of a motor reversed ?

A
  • swapping polarity of the dc supply

- swapping magnetic poles

71
Q

What does an induced current generate ?

A

A magnetic field that opposes the original change

Either movement of the conductor or the change in magnetic field

72
Q

How do u change the size of the induced potential difference ?

A
  • increase the speed of movement

- increase the strength of the magnetic field

physics (4 decks)

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