Magnetic Materials, Properties, and Magnetic Fields

Flashcards testing concepts of magnetism, magnetic vs non-magnetic materials, magnetic poles, induced magnetism, temporary vs permanent magnets, and magnetic field lines based on the lecture notes.

What is magnetism?

Magnetism is a force that acts at a distance upon magnetic materials.

What is the difference between magnetic materials and non-magnetic materials?

Magnetic materials are attracted to magnets (such as iron, nickel, and cobalt), while non-magnetic materials are not attracted by magnets (such as brass, copper, wood, glass, and plastic).

What is lodestone or magnetite, and what historical importance does it hold?

Lodestone (magnetite) is a rock discovered by the Greeks over 1000 years ago that attracts iron and always settles in a north-south direction when suspended freely, forming the basis of navigation compasses.

How does Activity 2 demonstrate magnetic force without direct contact?

Moving a magnet beneath card paper or glass causes scattered iron filings on top to follow its movement, showing that magnets attract objects containing iron even without direct contact.

How are the north and south magnetic poles of a bar magnet defined?

When a bar magnet is suspended horizontally and allowed to come to rest, the end that points north is the north magnetic pole (N), and the end that points south is the south magnetic pole (S).

What is the law of attraction and repulsion between magnetic poles?

Like magnetic poles repel each other (north repels north, south repels south), while unlike magnetic poles attract each other (north attracts south).

Why is repulsion considered the real test to identify a magnet?

Attraction can occur between opposite poles or between a magnet and an unmagnetized magnetic material, but repulsion only occurs between like poles of two magnets.

Is it possible to isolate a single magnetic pole by breaking a magnet?

No, breaking a bar magnet produces smaller complete magnets, each having both a north pole (N) and a south pole (S). Isolated poles do not exist.

What is induced magnetism (magnetization)?

Induced magnetism is the process by which a magnetic material (such as iron or steel) is made into a magnet when brought near or in contact with a true magnet.

What polarities are induced at the near and far ends of an iron piece placed near a magnet's S-pole?

The S-pole of the true magnet induces an opposite N-pole in the near end of the iron piece and a like S-pole in the far end.

What is a temporary magnet and what are some examples?

A temporary magnet works only in the presence of an external magnetic field and loses its magnetism when the field vanishes. Examples include soft iron, paper clips, office pins, iron nails, and electromagnets.

What is a permanent magnet and what materials are used to make one?

A permanent magnet retains its magnetic properties indefinitely. It is made from steel or special alloys such as cobalt, alnico, and ferrite.

How do iron nails and steel nails differ in their retention of induced magnetism?

Iron nails collapse immediately when the magnetic field is removed because their induced magnetism is temporary, whereas steel nails remain attached for some time because their induced magnetism is permanent.

What is a magnetic field?

A magnetic field is the region around a magnet where another magnetic object experiences a magnetic force.

What are magnetic lines of force and how do they behave around a bar magnet?

Magnetic lines of force represent the field pattern; they continuously move from the north pole (N-pole) to the south pole (S-pole) outside the magnet and never cross each other.

How is the direction of a magnetic field at a specific point defined?

The direction of the magnetic field at any point is defined as the direction indicated by the N-pole of a magnetic compass needle placed at that point.

Where is the magnetic field around a bar magnet the strongest?

The magnetic field is strongest near the poles where the magnetic lines of force are closest together.

What are two practical applications of permanent magnets?

Permanent magnets are used in magnetic strips on doors to keep them closed and in flourmills to remove iron particles from grains before grinding.

Magnetism

A force that acts at a distance to attract or repel magnetic materials.