A Beginner's View of Our Electric Universe - New

When operated, this switch allows a heavy current from the car’s
battery to flow to the starter motor which turns over the mechanical
working parts of the engine at the beginning of the engine’s start-up
process. One important thing to be aware of here is that the metal core
that became magnetic (magnetised) by the coil, was made to assume
a particular N-S polarity (north at one end and south at the other) and
that this effect was due to the DC from the battery flowing through the
coil in one direction only. This means we can consider passing current
in either direction through an electro-magnet’s coil to make it produce
both N-S or S-N polarities, as required. Depending on the mechanical
(or electrical) effect we want to achieve, this can even produce the
force of both magnetic attraction and repulsion in relation to some
external piece of equipment. There are clever ways in which we have
discovered how to employ this effect, certain types of electric motors being one, and bells, electric locks and
electro-magnetic brakes, being others.
The other type of magnetism we need to consider is the ‘fixed magnetism’ of a ‘permanent magnet’, the kind that
does not involve the flow of electric current and which is commonly associated with the ornamental paraphernalia
we stick on our fridge doors. Some materials, usually metals or composite materials with a metallic content, are
easily turned into permanent magnets by subjecting pre-shaped forms of that material to an external and very
strong magnetic field for a period of time. This process influences the atoms within the material to take on a
communally oriented direction that remains in place, giving the material an overall magnetic polarity, until such
time as the communal orientation of the atoms breaks down and the magnet loses its strength.
This ability of metals and compound materials to retain for some time the ‘permanent’ magnetisation they
have been endowed with, varies in terms of how magnetised they can be made to be, and for how long that
magnetisation can be retained. In addition to this being a description of the basic manufacturing approach to
creating permanent magnets, we now become aware that some materials are better at retaining their magnetisation
than others. For instance, steel is not very good at retaining magnetism but iron is much better, and the material
known as neodymium is exceptionally good at retaining its magnetisation. Neodymium is known as a ‘rareearth’
material that is used for many of the exceptionally strong magnets we see on the market these days.
There are some naming terms associated with the magnetic properties of material. ‘Permeability’ is the ease by
which materials are magnetised, ‘remanence’ is the ability to retain the magnetised state, and ‘coercivity’ is the
difficulty with which de-magnetisation is achieved. We do not need to remember these for our purpose here.
6 | Some basic theory that will help
Car starter switching circuit © author
Ignition Switch
Car Battery
Solenoid
(Electro-Magnet)
Starter Motor