What is a magnet?
A: A magnet is a material or object that produces a magnetic field.
This magnetic field is invisible but is responsible for
what property of a magnet?
A: A force that pulls on other ferromagnetic materials, such as iron, steel,
nickel, cobalt, etc. and attracts or repels other magnets.
A permanent magnet is an object made from a material
that is what?
A: Magnetized and creates its own persistent magnetic field.
What is an everyday example?
A: A refrigerator magnet used to hold notes on a refrigerator door.
Materials that can be magnetized, which are also the
ones that are strongly attracted to a magnet, are called what?
A: Ferromagnetic (or ferrimagnetic).
These include what elements?
A: Iron, nickel and cobalt and their alloys, some alloys of rare-earth
metals, and some naturally occurring minerals such as lodestone.
Although ferromagnetic (and ferrimagnetic) materials
are the only ones attracted to a magnet strongly enough to be commonly
considered magnetic, all other substances respond how to a magnetic field,
by one of several other types of magnetism?
A: Weakly.
Ferromagnetic materials can be divided into what two
types of material?
A: Soft materials like annealed iron, which can be magnetized but do not
tend to stay magnetized, and magnetically "hard" materials, which do.
Permanent magnets are made from "hard" ferromagnetic
materials such as what?
A: Alnico and ferrite.
The overall strength of a magnet is measured by what?
A: Its magnetic moment or, alternatively, the total magnetic flux it
produces.
The local strength of magnetism in a material is
measured by its what?
A: Magnetization.
When does a coil of wire act as a magnet?
A: When an electric current passes through it but stops being a magnet when
the current stops.
Often, the coil is wrapped around a core of what?
A: Soft ferromagnetic material such as mild steel, which greatly enhances
the magnetic field produced by the coil.
Ancient people learned about magnetism from what?
A: From lodestones (or magnetite) which are naturally magnetized pieces of
iron ore.
Lodestones, suspended so they could turn, were what?
A: The first magnetic compasses.
The earliest known surviving descriptions of magnets
and their properties are from where?
A: Anatolia, India, and China around 2500 years ago.
The properties of lodestones and their affinity for
iron were written of by whom?
A: Pliny the Elder in his encyclopedia Naturalis Historia.
By the 12th to 13th centuries AD, magnetic compasses
were used for what?
A: For navigation in China, Europe, the Arabian Peninsula and elsewhere.
If a bar magnet is broken into two pieces, in an
attempt to separate the north and south poles what happens?
A: The result will be two bar magnets, each of which has both a north and
south pole.