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Physical Science > Magnetism > Flashcards

Magnetism Flashcards

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1
Q

When was the magnetic effect of certain substances observed and by who

A

By the greeks in 800bc

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2
Q

What are ferromagnetic substances

A

Materials that are strongly attracted by magnets

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3
Q

What are the 3 ferromagnetic substances

A

Iron (Fe), nickel (Ni), cobalt (Co)

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4
Q

What are examples of substances are non-magnetic

A

Copper (Cu), Manganese (Mn), and tin(Sb)

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5
Q

What is a magnetic alloy

A

A mixture of a ferromagnetic substance and a non-magnetic substance in order to form a magnetic substance

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6
Q

Give examples of magnetic alloys

A

Ceramics is a mixture of iron and metal oxides eg. Fridge magnets
Alnico is a mixture of aluminium,nickel and cobalt eg in speakers
Steel is a mixture of iron and carbon eg in compasses

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7
Q

What are ferromagnetic Substances broken down into

A

Soft magnetic materials and hard magnetic materials

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8
Q

What are soft magnetic substances

A

Materials that can be magnetised(easily changed into a magnet) eg iron

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9
Q

Where are soft magnets used

A

Used as temporary magnets like in scrap yards, in speakers and in telephones

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10
Q

What are hard magnetic materials

A

Materials that take long to magnetise but reserves magnetism eg steel

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11
Q

What is the use of hard magnets

A

Used for permanent magnets and in compasses

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12
Q

What is the use of magnetic materials

A
  • A compass is a magnetic needle is free to move and it aligns with the magnetic field of the earth and points towards magnetic north
  • credit, debit and ATM cards have a magnetic strip on one side. This strip contains all the information of the account holder
  • loud speakers use magnets to convert electrical signals yo sounds that we can hear
  • hospitals use resonance image to identify problem in a persons organs without having to operate
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13
Q

What is a magnetic field

A

A region in space where another magnet or ferromagnetic magnetic material will experience a non-contact force

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14
Q

How does a magnetic field form

A

An electron has a charge of 1.6 x 10^-19 and circles the nucleus in about 10^-16 seconds which is equivalent to the electric current of 1,6 x 10^-3 Ampere. Thus an electric current causes a magnetic field at the centre of the circular path that the electrons follows.the magnetic field that is caused by an electron that moves in a circle us perpendicular to the circular motion. Each atom behaves like a small magnet, because of the motion of its electrons around the nucleus as its source of magnetism due to the magnetic field it causes.

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15
Q

How are non-magnetic substances formed if all atoms behave as small magnets

A

This is because in a non-magnetic substance the direction of the electron magnetic field moves in all directions so the net magnetic field is 0

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16
Q

Why are ferromagnetic substances magnetic

A

This is because they have small groups of atoms grouped together with their magnetic fields in one direction.

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17
Q

What is a magnetic domain/ magnetic area

A

A group of atoms with their magnetic fields in one directiob

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18
Q

What is the smallest l permanent magnet

A

A magnetic domain

19
Q

How is the domains in a permanent magnet

A

I’m a permanent magnet the domains move and align with the magnetic field and that results in a nett magnetic field

20
Q

What properties do magnetic field lines have

A
  • Magnetic field lines are imaginary and do not really exists
  • magnetic field lines are three dimensional lines, the magnetic field is all around the magnet and so also the magnetic field lines that represent the magnetic field.
  • magnetic field lines never cross each other
  • magnetic field lines Indicate the force on a North Pole of a magnet And thus always point away from the north pole to the South Pole .
  • Inside the magnet bar the magnetic field lines show from south to north.
  • Arrows on the magnetic field show the direction of the magnetic field
  • the closer the magnetic fields are to each other the stronger the magnetic field. Where the magnetic field is weak the magnetic field lines are further from each other
21
Q

Explain the poles of a magnet

A

Because the domains in a permanent magnet all arrange themselves in a specific direction, the magnet has a pair of opposite piles, that we call a north and South Pole.

22
Q

How do you magnetise ferromagnetic substances

A

By brushing along the object with a magnet in one direction. This causes the magnetic field of most of the domains to align and Point in the same direction. As a result the object will have, as a whole, a nett magnetic field. It is magnetised.

23
Q

Under what condition does a ferromagnetic substance stay a magnet

A

As long as there isn’t another magnet nearby it

24
Q

Where is the magnetic field of a magnet the strongest

A

At the Poles

25
Q

What is a magnetic field on a microscopic level

A

The motion of charges

26
Q

What defines the geographic poles

A

The movement of the sun, these poles are two points on the earth that experience no sunset or sunrise. For six months of the year the sun is always above the horizon and for the other six below the horizon

27
Q

What are the current magnetic north and south

A

North Canada is the magnetic north and Antarctica is the magnetic south

28
Q

What is the angle between the lines the connect the geographic and magnetic north and south and what is it known as

A

11.5 degrees and it is known as the angle of declination

29
Q

How many kilometres does the magnetic North Pole move per year

A

About 40 I’m

30
Q

Which animals use the earths magnetic field to determine direction

A

Doves, bees, monarch butterflies, sea turtles and fish have small amounts of ferromagnetic substances in them and thus are able to locate the earths magnetic field to orientate themselves and determine their direction.

31
Q

What is the magnetosphere

A

The earths magnetic field that spreads out far above the earth.

32
Q

What does the magnetosphere do

A

It protects the earth from high speed charged particles that tumble to the earth from the sun, called solar wind. These particles can move at a speed of 400 km per second and cause great damage to form of life as well as telecommunications on earth.

33
Q

Is the earths magnetic field lines symmetrical ? Why ?

A

No this is because the magnetic field lines that point the sun are compacted by the solar wind while magnetic field lines that point away from the sun are more stretched out and form a magneto tail.

34
Q

How much space does the magnetosphere occupy

A

80-60 000km on the side facing the sun and up to 300 000km of the side that stretches away from the sun.

35
Q

What is the bow shock

A

The curve that the solar wind is forced around the earth when it comes into contact with the earths magnetic field

36
Q

How does an Aurora form

A

When the particles of the solar wind from the sun enter the earths magnetic field and are trapped. These particles collide with the air molecules in the upper atmosphere and ionise the air molecules. As the air molecules are ionised they radiate energy in the form of light that are observed as flashed of dancing light known As an Aurora

37
Q

Where can you observe an Aurora

A

Near the earths magnetic poles. By Alaska and Norway they are called the northern lights (Aurora borealis) by Antarctica they are called the southern lights (Aurora Australis)

38
Q

What is a magnet

A

A piece of metal that pulls other metal objects towards it. The magnet can hold those objects or even make them move.

39
Q

What is magnetism

A

The pulling force of the magnet

40
Q

What causes the earths magnetic field

A

It is caused by the Iron in the earths core.

41
Q

Explain how a compass needle indicated the direction of a magnetic field

A

A compass needle is a small magnet when the compass needle is placed near a magnet, its magnetic north points towards the geographical north. The compass needled north points towards the South Pole of the magnet

42
Q

Explain the difference between the earths geographic North Pole and the magnetic North Pole of the earth

A

The earth has two geographical poles. These two poles are points on the earths surface where the line of the earths axis of rotation meets the earths surface. The angle between the lines that connect geographical North-South and the magnetic North-South where a compass needle points is 11.5° which is known as the angle of declination.

43
Q

What is the source of electromagnetic radiation

A

The acceleration of charged particles

44
Q

Electromagnetic radiation is said to have dual nature. What does this mean

A

Electromagnetic radiation can behave as a particle as well as a wave

Physical Science (29 decks)

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