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Physics > Chapter 9 (9.1 - 9.8) - Magnetism > Flashcards

Chapter 9 (9.1 - 9.8) - Magnetism Flashcards

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1
Q

What are poles of a magnet

A

Points of the magnet where the magnetic force originates from

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2
Q

What happens to like poles
What happens to unlike poles

A

Like poles - repel
Unlike poles - attract

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3
Q

Relationship between force between poles and distance

A

Inversely proportional. As distance decreases, force between the poles increases.

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4
Q

Why are metals attracted to magnets

A

Induced magnetism - when a magnet is nearby, the metal itself becomes a magnet with unlike poles to the original magnet. This leads to the metal being attracted.

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5
Q

What is a permanent magnet
eg

A

Keeps some of its induced magnetism even after its pulled away from the magnet
eg steel

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6
Q

What is a temporary magnet
eg

A

Loses all its induced magnetism after it is pulled away from the magnet
eg iron

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7
Q

2 ways to make a magnet

which is more effective

A

Stroke the metal with the magnet
Put the metal in a metal coil and pass a one way current through it (dc)

Current method is more effective

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8
Q

What are magnetic materials (definition)

mention the 2 types

A

Can be magnetized and is attracted to magnets

2 types:
hard
soft

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9
Q

What are ferromagnetics

A

Strongly magnetic materials

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10
Q

Explain what hard magnetic materials are
eg and use case(s)

A

Materials that are difficult to magnetize but do not readily lose their magnetism
eg: steel, alcomax
use: permanent magnets

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11
Q

Explain what soft magnetic materials are
eg and use case(s)

A

Materials that are relatively easy to magnetize but their magneitsm is temporary
eg: iron, mumetal
use: electromagnets and transformers

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12
Q

How to demagnetize a mateiral

A

Hammer it repeatedly
heat it to a high temp
Pull out of a coil with AC current flowing thru it

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13
Q

What is the magnetic field

A

Region around the magnet that exerts a force on the magnetic materials in it

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14
Q

What is the neutral point

A

Point between 2 like poles where the field lines exactly cancel eachother out and the magnetic force is 0

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15
Q

What happens to the magnetic field lines if two poles are placed near each other

A

Magnetic fields combine with each other to produce a single field.

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16
Q

What happens when a current is passed through a wire

A

A weak magnetic field is produced

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17
Q

Properties of magnetic field when current is passed through a wire

A

Magnetic field lines are circled
Field lines are strongest closet to the wire
Increasing the current would increase the strength of the field

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18
Q

What is the rule for finding field direction when a current is passed through a wire
what shows what

A

Right-hand thumb rule.
Thumb points in the direction of the conventional current
Fingers point in the same direction as field lines

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19
Q

What is a solenoid

A

A long coil

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20
Q

Magnetic field produced in a single coil vs solenoid (properties)

A

Magnetic field is strong in solenoid since there are more coils

Increasing the current would increase the magnetic field produced

Same field lines as a bar magnet

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21
Q

Components of an electromagnet

A

A coil (usually copper)
A core (usually iron)

22
Q

Why does an electro magnet work

A

When current is passed through a coil, a weak magnetic field is generated. This magnetisezes the core (induced) which creates a much more powerful magnetic field than jus the coil alone

23
Q

How to increase strength of magnetic field

A

Increasing current
Increasing number turns in coil

24
Q

Why is a force generated when a current is passed through a wire which is in an electric field

what rule is used to find the direction of the force
acronym

A

The current produces its own magnetic field which acts upon the poles of the magnet, generating a force.

Fleming’s Left hand rule
FBI (force, direction of magnetic field, direction of current)

25
Q

What happens to a beam of charged particles (eg electrons) as they pass a magnetic field

A

A force acts upon them

eg current

26
Q

When does flemings left hand rule not work

A

When the current and field are in the same direction, there is no force thus the rule doesnt work

27
Q

What is the turning effect on a coil

A

When a rectangular coil is in between a magnetic field and a current is passed through it a turning effect is generated. This is because the current travels in opposite directions at either end of the coil, pushing one side up and one side down

28
Q

How to increase the turning effect on a coil

A

Increase the number of turns in the coil

29
Q

Components of a DC motor

A

Battery
Brushes
Split ring
Coil
Magnet

30
Q

What does a split ring do
aka

A

Changes the direction of the current so that the force changes direction and the coil continues to rotate
Commutator

31
Q

When does the coil have maximum turning effect (DC motor)

A

When it is horizontal

32
Q

How to increase the turning effect of coil in DC motor

A

Increase area of coil
Stronger current
More number of turns in the coil
Stronger magnet

33
Q

What is electromagnetic induction

what happens

A

Induction of current as wire moves across a magnetic field

an EMF is induced

34
Q

What is a galvanometer

A

A meter that is sensitive to very small currents.

35
Q

How to increase induced EMF

A

Move wire faster
Use a stronger magnet
increase length of wire in the magnetic field (eg: looping the wire)

36
Q

What is Faraday’s law

A

The emf induced in a conductor is proportional to the rate at which magnetic field lines are cut by the conductor

37
Q

How to reverse the direction of the induced emf

A

Move the wire in the opposite direction
Turn the magnet around so that the field direction is reversed

38
Q

When is there no induced emf

A

When the wire is not moving
When the wire is moving parallel to the magnet field lines (not cutting)

39
Q

Why is there an induced EMF when a bar magnet is pushed into a coil

A

Magnetic field lines are still being cut by the wire as the bar magnet moves in and out of the coil.

40
Q

How to increase the induced EMF of a magnet being pushed into a coil

A

Move the magnet faster
Use a stronger magnet
Increase number of turns in the coil (increases the length of the wire cutting through the magnetic field)

41
Q

When is the direction of induced emf (and current) reversed between a bar magnet and a coil

A

When the magnet is pulled out
When the south pole is pushed in instead of the north

42
Q

When is there no induced EMF between a magnet and the coil

A

When the magnet is held still (no field lines are being cut)

43
Q

What is lenz’s law

A

Induced current always flows in a direction such that it opposes the change that produced it

44
Q

What does fleming’s right hand rule find

what shows what

A

Direction of induced current

thumb - motion
index - field
middle finger - induced current

45
Q

When does fleming’s left hand rule apply
when does fleming’s right hand rule apply

A

Left: When current causes motion
Right: When motion causes current

46
Q

which component is the ac generator connected to

A

primary coil

47
Q

what are brushes used for

A

prevents friction, prevents loss of current

48
Q

Where are split rings used
where are slip rings used

A

slip - generator
split - dc motor

49
Q

how do electrons move

A

negative to positive

50
Q

how does current move

A

positive to negative

51
Q

how do compasses tilt

A

align with magnetic field lines
points to south if field lines move from N to S

Physics (25 decks)

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