CHAPTER 15. MAGNETISM

Magnetism

15

Introduction ESAEF

Magnetism is an interaction that allows cer-

tain kinds of objects, which are called ‘mag-

netic’ objects, to exert forces on each other

without physically touching. A magnetic ob-

ject is surrounded by a magnetic ‘field’ that

gets weaker as one moves further away from

the object. A second object can feel a mag-

netic force from the first object because it

feels the magnetic field of the first object. The

further away the objects are the weaker the

magnetic force will be.

See introductory video: ( Video: VPfkk at

http://www.everythingscience.co.za)

Humans have known about magnetism for

many thousands of years. For example,lode-

stoneis a magnetised form of the iron oxide

mineralmagnetite. It has the property of at-

tracting iron objects. It is referred to in old

European and Asian historical records; from

around 800 BCE in Europe and around 2 600

BCE in Asia.

Magnetic objects stuck to a magnet

Photograph by dougww on Flickr.com

FACT

The root of the En-

glish wordmagnetis

from the Greek word

magnes, probably

from Magnesia in

Asia Minor, once an

important source of

lodestone.

Magnetic fields ESAEG

A magnetic field is a region in space where a magnet or object made of magnetic material

will experience a non-contact, magnetic force.

A moving charged particle has a magnetic fields associated with it. One example of a

charged particle that occurs in most matter is the electron. Electrons are in constant motion

inside material, orbiting the nucleus in the atom which may also be moving, rotating or

vibrating.

Physics: Electricity and Magnetism 245