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⭐️raj vigya > magnetism, electro magnetism > Flashcards

magnetism, electro magnetism Flashcards

1
Q

when and where were the first stones with magnetic properties found

A

around 600 bc in magnesia in asia minor (present day turkey)

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2
Q

what kind of stones were the magnets

A

oxides of iron called magnetite

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3
Q

what is the formula for magnetite

A

Fe3O4

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4
Q

what is another name for magnetite

A

lodestone

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5
Q

which properties of magnets are called magnetism

A

when hanging freely, they always stay along the north-south direction, and attract or repel each other. these properties are called magnetism

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6
Q

what are natural magnets

A

naturally occurring magnets like magnetite

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7
Q

what are artificial magnets

A

made from different components of iron in various shapes and sizes for different uses

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8
Q

give a few examples of shapes of artificial magnets

A

bar magnet
horse shoe
magnetic compass
cylindrical
electromagnet

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9
Q

which magnet was used in magnetic compass for the first time

A

the natural lodestone

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10
Q

which kind of artificial magnet is a temporary magnet

A

electromagnet

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11
Q

where is the magnetism highest and lowest in magnets

A

highest at poles
zero in centre

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12
Q

what is the neutral point of magnets

A

the centre where there is no magnetism

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13
Q

which experiment shows that the poles cannot be separated from magnets

A

when magnet is broken, each piece becomes a new magnet and has two poles

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14
Q

when does iron act as a magnet

A

when brought near a powerful magnet

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15
Q

what are the types of magnetic materials

A

para magnetic
dia magnetic
ferro magnetic

another one are antiferromagnetic, dekhenge uspe jana hoga to

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16
Q

what are para magnetic materials

A

materials which are not strongly attracted to a magnet

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17
Q

what happens to para magnetic materials in an external magnetic field?

A

they acquire weak magnetism in the direction of fiels

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18
Q

examples of paramagnetic materials

A

platinum aluminium
sodium manganes
oxygen and even air

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19
Q

usually in which kind of substances based on their electron configuration is para magnetism observed?

A

in those substances whose atoms have an odd number of electrons

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20
Q

which instrument is used to detect the flow of current

A

moving coil galvanometer

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21
Q

what are dia magnetic materials

A

those which are repelled by a magnet

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22
Q

what happens to dia magnetic materials in an external magnetic field

A

they acquire weak magnetism in the opposite direction of the field

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23
Q

examples of dia magnetic materials?

A

bismuth, lead, water, gold, silver, nitrogen, diamond, hydrogen etc

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24
Q

what are ferromagnetic materials

A

those which are strongly attracted to magnets
Eg iron, cobalt, nickel etc or magnetite or alloys

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25
Q

what happens to ferromagnetic materials in an external magnetic field

A

become strongly magnetized in the direction of the field and when brought near the end of a magnet, are strongly attracted towards the ends

26
Q

what does domains theory explain

A

why any substance has the property of magnetism

27
Q

what is a domain in domains theory

A

a small local region in which all the magnetic dipoles align parallel to each other giving rise to certain magnetisation within the domain

28
Q

according to domains theory, why is the net magnetisation of a specimen as a whole is zero

A

because within a domain, the magnetisation is different from the neighboring domain, as a result, the net magnetisation is zero

29
Q

what happens to a domain when a substance is magnetised

A

the domain expands in space such that all the arrows align parallel to each other in a single direction

30
Q

what kind of domains would an ideal magnet produce

A

a single domain with all molecular magnets pointing in one direction

31
Q

how does an electron acts like a microscopic magnet

A

spinning motion of electron generates an electric current

32
Q

how does an atom has no net magnetic charge

A

if a few electrons are spinning clockwise and same number are spinning anti clock wise, then the magnetic moments cancel each other out

33
Q

in which case an atom start to carry a magnetic field and would react to external magnets

A

if there are unpaired electrons

34
Q

magnetic field around an atom depends on?

A

the number of unpaired eletrons in the atom

35
Q

in what kind of magnetic materials, each atom behaves like a miniature magnet

A

ferromagnetic

36
Q

what is a domain in a ferromagnetic material

A

in ferromagnetism, some complex and reciprocal actions take place in these atoms which results in formation of numerous microscopic effective field in the material in the magnetic axis of these effective fields alinged unidirectionally, these fields are called domains

37
Q

how many atoms does a domain consist of

A

10^18 to 10^21

38
Q

what happens to the domains to give the magnetic properties to ferromagnetic materials

A

mutual substitution and rotation of domains

39
Q

why is the net magnetic moment in any direction is zero according to domains theory

A

these domains are scattered randomly in the materials in such a way that in any direction the net magnetism is zero

40
Q

how do ferromagnetic materials gain permanent magnet characteristics according to domain theory?

A

when it is placed in an external magnetic fiels, the external magnetic field force it to align in its own direction. this force mobilise the doain and they arrange themselves in the direction of applied external magnetic fiels. thus forming large single domain with magnetism in the direction of the external magnetic field. that is how ferromagnetic materials gain the properties of permanent magnets

41
Q

what happens when a magnet or ferromagnetic material is heated

A

at its absolute temperature, the magnetic property gets destroyed

42
Q

what is curie’s law of magnetism

A

the magnetic characteristics of a ferromagnetic material is inversely proportional to its absolute temperature.

43
Q

what is curie temperature

A

on increasing the temperature, a point comes at which due to thermal disturbance, its ferromagnetic property is destroyed and it becomes para magnetic. this is the curie temperature

44
Q

what is the curie temperature of iron vs magnetite

A

770 deg c and 570 deg c

45
Q

what is the curie temp of nickle

A

358 deg c

46
Q

what is the direction of magnetic field lines

A

emerging from north pole and end at south

47
Q

when do magnetic lines of force emerge from south and end at north?

A

never
always north to south

48
Q

how often do magnetic field lines intersect each other

A

never

49
Q

what kind of loops do magnetic field lines form

A

closed loop

50
Q

if the magnetic field is uniform, what does it signify for lines of force

A

that they are parallel to each other and at equal distances

51
Q

how can we see through magnetic field lines that the force at poles is the strongest

A

magnetic field lines are very close at poles

52
Q

what happens to the density of magnetic force lines when a magnetic material is placed in a magnetic field

A

when magnetic substance like a soft iron rod is placed in a magnetic field, the density of the magnetic force of lines inside the rod increases as compared to outside

53
Q

what happens to the density of magnetic force lines when a non magnetic material is placed in a magnetic field

A

when non magnetic substance like aluminum is placed in a magnetic field, the density of the magnetic force of lines inside the rod decreases as compared to outside

54
Q

what is magnetic permeability

A

the conducting property of matter due to which density of magnetic lines of force inside it increases or decreases is called magnetic permeability

55
Q

by which symbol is magnetic permeability denoted

A

µ

56
Q

formula for magnetic permeability?

A

µ=B/H

B= number of lines of force/sq meter of magnetic materialH= number of lines of force/sq meter of air

57
Q

what is the unit of magnetic permeability

A

henry/meter

58
Q

what is magnetic susceptibility

A

property of a substance that describes how easily the substance acquires magnetic property is called

59
Q

what is the formula for magnetic susceptibility

A

X=I/H=K(constant)

I= magnetic intensity in the material
H=value of the force magnetizing the material

60
Q

what is the magnetic susceptibility constant called

A

Chi(kai)

⭐️raj vigya (23 decks)

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