P7:Magnetism & Electromagnetism Flashcards Preview

GCSE PHYSICS AQA (PAPER 2) > P7:Magnetism & Electromagnetism > Flashcards

Flashcards in P7:Magnetism & Electromagnetism Deck (65):
1

All magnets have two poles...

•North (or north seeking)
•South (or south seeking)

2

All magnets produce a...

Magnetic field ( a region where other magnets or magnetic materials experience a non-contact force)

3

You can show a magnetic field by drawing...

Magnetic field lines
Page 227
•Lines always go from north to south and they show which way the force
•The closer together the lines are, the stronger the magnetic field
•The further away from the magnet, the weaker the field is

4

The magnetic field is always...

Strongest at the piles of the magnetic, meaning the magnetic forces are strongest at the poles

5

The force between a magnet and magnetic material is...

Always attractive

6

If two piles of a magnet are out near each other...

They will each exert a force in each other.

7

An exerted Force can be...

Attractive or repulsive.

8

Two poles which are the same will...

Repel each other

9

Two unlike poles will...

Attract each other

10

Inside a compass is a tiny bar magnet, the North Pole If this magnet is...

Attracted to the South Pole of any other magnet it’s near, the compass points in the direction of the magnetic field it is in

11

You can move a compass around a magnet and...

Trace it’s position in some paper to build up a picture of what the magnetic field looks like

12

When compasses aren’t near a magnet, they always point north because...

The earth generates its own magnetic field, which shows the inside (core) of the earth must be magnetic

13

There are two types of magnets...

Permanent and induced

14

Permanent magnets...

Produce their own magnetic field

15

Induced magnets...

Are magnetic materials that turn into a magnet when they are out into a magnetic field

16

The force between permanent and induced magnets are...

Always attractive

17

When you take aways the magnetic field, induced magnets...

Quickly lose their magnetism (or most of it) and it stops producing a magnetic field

18

When a current flows through a wire...

A magnetic field is created around the wire

19

The field in a moving charge is made up of...

Concentric circles perpendicular to the wire, with the wire in the centre. You can see this by placing a compass near a wire that is carrying a current. As you move the compass, it will revise the direction of the magnetic field

20

Changing the direction of the current changes...

The direction of the magnetic fields, use the right hand thumb rule to figure out which way it goes

21

The right hand thumb rule...

Using your right hand, point your thumb in the direction of current and curl your fingers, the direction of your fingers is the direction of the field

22

The strength of the magnetic field produces changes with the current and the distance from the wire...

The larger the current through the wire, or the closer to the wire you are, the stronger the field is

23

You can increase the strength of the magnetic field that a wire produces by...

Wrapping the wire into a coil called a solenoid. This happens because the field lines around each loop of wire line up with each other

24

The solenoid results in lots of field lines pointing in the same direction...

That a very close to each other, the closer the field lines are, the stronger the field is

25

The magnetic field inside a solenoid is...

Stronger and uniform. It has the same strength and direction at every point in that region. Outside the coil, the magnetic field is just like the one around the bar magnet

26

The ends of a solenoid act like the North Pole and South Pole If a bar magnet...

You can work out which end of the solenoid is the North Pole and which is the South Pole using the right hand rule

27

You can increase the field strength of the solenoid even more by...

Putting a block of iron in the centre of the coil. The iron core becomes an induced magnet whenever current is flowing

28

If you stop the current, the magnetic field disappears...

A solenoid with an iron core is called an electromagnet

29

A solenoid with an iron core is a...

Magnet whose magnetic field can be turned on and off with an electric current. It consists of an insulated wire wrapped around an iron bar

30

On an electromagnetic field, if you’re looking from a birds eye view if there’s a dot...

The current is going out of the page

31

On an electromagnetic field, if you’re looking from a birds eye view if there’s a cross...

The current is going into the page

32

The magnetic field lines around a wire are circles centres on the wire in a....

Plane perpendicular to the wire

33

The magnetic field lines in the solenoid are parallel to its axis and are all in the same direction...

A uniform magnetic field is one which the magnetic field lines are parallel

34

Increasing the current makes the magnetic field stronger, reversing...

The direction of the current reversed the magnetic field

35

When a current carrying wire or any other conductor is put between magnetic poles, the magnetic friend around the wire...

Interacts with the magnetic field it has been place in. This causes the magnet and the conductor to exert a force in each other, this is called the motor effect

36

The motor effect can cause...

The wire to move

37

To experience the full force, the wire has to be 90 degrees to the magnetic field...

If the wire runs parallel to the magnetic field, it won’t experience any force at all. At angles in between, it will feel some force

38

The force always acts at right angles to the magnetic field of the...

Magnets and the direction of the current in the wire

39

A good way of showing the direction of the force is to apply a current...

To a set of rails inside a horse shoe magnet. A bar is placed on the rails, which completes the circuit. This generates a force that rolls the bar along the rails

40

The magnitude of the force...

Increases the strength of the magnetic field

41

The force also increases with the...

Amount of current passing through the conductor

42

The force acting on a conductor in a magnetic field depends on...

•The magnetic flux density, how many field (flux) lines there are in the region. This shows the strength of the magnetic field
•This size of the current through the conductor
•The length of the conductor that’s in the magnetic field

43

When the current is at 90 degrees to the magnetic field it is in....

The force acting on it can be found using the F = BIL equation

44

F = B I L

Force (N) = magnetic flux density (T, Tesla) x current (A) x length (M)

45

You can find the direction of this force with Flemings left-hand rule...

•Using your left hand, point your First finger in the direction of the magnetic Field
•Point your seCond finger in the direction of the Current
•Your thuMb will then point in the direction of the force/ Motion

46

Flemings left hand tile shows that if either the current or the magnetic field is reversed...

Then the direction of the force will also be reversed, this can be used for all sorts of things like motors

47

1)A basic dc motor, forces act on the two side arms of a coil of wire that’s carrying a current
2)These forces are just the usual forces which act on any current in a magnetic field, because the coil is on a spindle and the forces act one up and one down, it rotates
3)The split ring commutator is a clever way of swapping the contacts every half turn to keep the motor rotating in the same direction...

4)The direction of the motor can be reversed either by swapping the polarity if the dc supply (reversing the current) or swapping the magnetic poles over (reversing the field)
5)The speed of the motor can be increased by increasing the current, adding more turns to the coil for increasing the magnetic flux density
6)you can use Flemings left-hand rule to work out which way the coil would turn

48

The optical density of a material is a measure of how quickly...

Light can travel through it, the higher the optical density, the slower light waves travels through it

49

How much the wave is refracted by depends on how much the wave speeds up or slows down, which usually depends on...

The density of the two materials, for example the higher the density of a material, the slower a wave travels through it

50

In a refracted light ray diagram, if the second material is optically denser than the first...

The refracted ray bends towards the normal, and the angle of refraction is smaller than the angle of incidence

51

When transmitted radio waves reach the receiver, the radio waves are absorbed. The energy carried by the waves is transferred to the electrons in the material of the receiver...


This energy causes the electrons to oscillate and, if the receiver is part of a complete electrical circuit, it generates an alternating current. This current has the same frequency as the radio wave that generated it

52

When a wave crosses a boundary at an angle, only part of a wave front crosses the boundary at first...

If it’s travelling into a fender material, that part travels slower than the rest of the wave front

53

In a refracted light ray diagram, if the second material is less optically dense...

The angle of refraction is larger than the angle of incidence

54

Rays are straight lines that are perpendicular to wave fronts...

They show the direction a wave is travelling in

55

A wave front is a line showing all of the points on a wave that are...

In the same position as each other after a given number of wavelengths

56

By the time the while wave front crosses the boundary, the faster pasty if the wave front will have travelled...

Further than the slower part of the wave front.

57

When a wave crosses a boundary between...

Two materials it changes

58

If the wave is travelling along the normal...

It will change speed, but it’s NOT refracted

59

If the wave hits the boundary ay an angle...

It changes direction and is refracted

60

The wave will bend towards the normal if...

It slows down

61

The wave will bend away from the normal if...

It speeds up

62

The frequency of the waves produced will be...


Equal to the frequency of the alternating current

63

Alternating currents (ac) are made up of oscillating charges. As the charges oscillate...

They produce oscillating electric and magnetic fields

64

EM waves are made up of...

Oscillating electric and magnetic fields

65

It’s the difference in the distance travelled (caused by the difference in speed)...

By the wave front causers the wave to bend (refract)