by Ian Loft

Created on: September 07, 2008

In the early 1990's I worked in a power station where my job required frequent excursions into the generator room, inside control booths, behind the alternators and around the huge power bus bars carrying many hundreds of amps of electric current. I soon learned to leave my wallet in which credit cards and electronic identification cards on which magnetic strips activated various readers locked in my desk draw because proximity to power generating equipment and high currents exposed them to electromagnetic fields and they became very quickly corrupted.

Few people today realise the importance of magnetic fields and their underpinning of almost all electronic applications in today's world of gadgets, automatic functions, motors, generators, transformers, decoders, electronic filters and speakers just to name a few. Each of these devices or appliances incorporate magnetic fields in various ways and at different frequencies, for example speakers are designed to operate across a limited range of audio signals while a transformer employs the fundamental principle of mutual induction that enables us the ability to boost or reduce power and current.

So what is a magnetic (electromagnetic) field? In simple terms it is possible to visualise a magnetic field by comparing it to a stream of water. The current flows in one direction and vary in strength much as a magnetic field can vary in strength, and where the direction of flow is from north and south poles. This can be demonstrated using a bar magnet and fine iron filings scattered on a piece of paper. Place the magnet under your paper and scatter filings across the top. As you rotate the magnet underneath you will see the field shape and orientation by the way filings line up and form around the magnet shape.

An electromagnetic field is simply a field induced by way of applying electrical current. In the wire itself an electromagnetic field surrounds the core and this field can be increased to incredible strengths by winding the conductor around an iron core. Ever dropped a small screw down an inaccessible place and wondered how to retrieve it? Try this: find a length of find insulated wire say about four or five feet in length. Wrap it tightly around a long screwdriver and use a little sticky tape to hold it in position. Ensure both ends come out close to the handle; you can wind the wire up and down in several layers to increase the power. Bare ends and clamp, screw or solder them to a battery holder (AA size is sufficient),

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