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3° MAGNETS

What is a Magnet?

A bar magnet and its field lines.A magnet is an object or a device that gives off an external magnetic field. Basically, it applies a force over a distance on other magnets, electrical currents, beams of charge, circuits, or magnetic materials. Magnetism can even be caused by electrical currents. 

There are many different types of magnetic materials. Iron (Fe) is an easy material to use. 

 There are many different types of magnets. Permanent magnets never lose their magnetism. There are materials in the world that are called ferromagnetic. Those materials are able to create and hold a specific alignment of their atoms. Since many atoms have amagnetic moment (tiny magnetic field), all of the moments can add up to create a magnet. Scientists use the word hysteresis to describe the way the atoms stay aligned. 

Most of the magnets you see around you are man-made. 




Electricity can make magnets
Current in wires produces a magnetic effect.
You can increase the strength of that magnetic field by increasing the current through the wire. We can use this principle to make artificial, adjustable magnets called electromagnets, by making coils of wire, and then passing current through the coils. 
Electromagnets  have a ferromagnetic material (usually iron or steel) located inside of the coils of wire. 
Electromagnets can be turned on and off. They both depend on currents of electricity to give them magnetic characteristics. Not only can they be turned on and off, but they can also be made much stronger than ordinary magnets. You might see an electromagnet at work in a junkyard lifting old cars off the ground. 





Magnets can make electricity

Faraday's law of induction is one of the important concepts of electricity. It looks at the way changing magnetic fields can cause current to flow in wires. Basically, it is a formula/concept that describes how potential difference (voltage difference) is created and how much is created. It's a huge concept to understand that the changing of a magnetic field can create voltage. 

LINK physics4kids

GENERATOR

LINK: MOVIE How AC Generator Produces Electricity?


TRANSFORMER

The output voltage of a transformer is:

Vo = Vi(No/Ni)
where
  • Vo is the output voltage
  • Vi is the input voltage
  • No is the number of turns in the secondary coil
  • Ni is the number of turns in the primary coil
In the example of increasing the voltage, this formula can also written as:
Vo/Vi = No/Ni





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