Magnets – Fields, Poles, Turning Motors

what is a magnetHave you ever looked at a piece of equipment and wondered how it was rotating? Such as, what is making that fan turn? Most likely a motor of some sort is making that equipment or machinery turn, somewhere. A motor could be connected directly, called a direct drive, to the machinery. Or, it can be connected with maybe a sheave and belt arrangement. Yeah?

But what makes those motors turn? This post is going to go over not how motors work, but actually, physically what makes them turn or rotate in the first place.

A motor turns basically because of magnets and fields, and the arrangement of poles, and this is what I’d like to go over. I’m thinking this post on magnets will make up like a larger piece of motor theory. So motor theory will be the large topic, and magnets will be a sub-topic. And magnets are the root of motor motion so is also where we should start.

Hopefully, when you are at the bottom of this page, you will know properties of magnets and also some magnetism principles.

If you were to stop and look around on a busy corner, and truly grasp what was in front of you, you’d see so many motors in action. From vehicles, to fans, the coffee grinder motor at Starbucks has a motor with magnets that must follow the same principles as every other. An infinite number of pieces of electrical equipment operate because of like the collection of these rules and laws – that could be called magnetism.

All motors and power generating “motors”, run on magnetism. You ready?



What Is A Magnetic Material?

It’s probably important that we start here and lay the groundwork or foundation for motor theory by talking about magnetic materials. It may seem like kid stuff and you already know it, but magnets are well, awesome and fun to play with so get off your high horse. You too cool to play with magnets and iron shavings?

Whoa. Where did that come from?

Bits of metal being able to attract other pieces of metal is what magnetism is.

Iron and steel, steel is made from iron, have the ability to be magnetic. Other metals can be magnetic too but usually a little bit less. Other magnetic metals are cobalt and nickel. You can combine magnetic materials and make an alloy that possesses much more magnetic strength.

Here is where we get a little more into the non-kid stuff, the deep secrets about magnets. They are kind of trippy if you really think about them and their relationship with Earth that cannot be broken.

The magnetic effects concentrate the most in certain spots. Any guesses what these are called? You’ve heard it… Poles.

Magnetic Poles

how does a magnet work

Lines of force going from north to south. Always.

A magnet gets designated as having two poles. A north and south.

Here is the weird part. They are north and south because if you could freely suspend a magnet in the air, the poles on the magnet would line up with the direction on our motherland. For now, prior to me reading ahead and learning just like you, let’s assume that magnets align like this due to the natural electromagnetic waves that get emitted from Earth. We’ll find out later.

Whichever end of the magnet points north, is north. South, south. Ya dig?

Magnets – Permanent & Temporary

For our purposes, there is hard steel and soft steel.

If we were constructing a permanent magnet we may use hard steel.

Soft steel is easier to magnetize, however it only keeps a weak degree of magnetization when the force making it magnetic is removed, like say, electricity.

The small amount of magnetism that does remain is called residual magnetism. Residual magnetism is something we want and is vital to the principles of operation of electrical equipment.

Electromagnets

Here is where we kind of get into like old school science project stuff. Making a magnet, using electricity, basic wiring. It’s so much fun.

We can easily make a strong magnet by wrapping a coil of wire around a bar of soft steel and apply a current. Viola.

This is an electromagnet. When the current is interrupted, the strong magnetic force that was created initially gets reduced to a weaker residual force.



Magnetic Induction

We can also induce magnetism into objects by placing them next to a magnet. You’ve probably done this experiment in science with a magnet and paperclips.

This is called induced magnetism. When we use soft steel, the magnetism we can induce is temporary, making it a temporary magnet, but remember the smaller amount of residual left. As soon as we remove the nearby magnet, the magnetism is gone. Like a thief in the night.

Magnetic Fields
magnetic field and lines of force

See how the iron shavings line up naturally?

Magnets have the ability to influence each other from a distance without having to physically be in contact. I would imagine the magnetic material and distance would impact the strength of a magnetic field.

The invisible area around the magnet with which this force acts is called the magnetic field. I believe scientists long ago had trouble imaging these concepts so they used like drawing concepts to “show” how the force must flow between poles. The lines can be referred to as magnetic lines of force and they exist between the poles.

All of the invisible lines are called magnetic flux.

Magnetic lines of force can’t be insulated from or blocked and can pass through, around, or within any material.

Magnetic Field Strength

How the lines of force concentrate provides us with an indication of the magnetic strength in a magnetic field.

If we measure the number of flux lines in a given area, we can find out the concentration. How much concentration is called flux density.

  • As the number of flux lines increase in the same area, the stronger the magnetic field.
Magnetic Flux Properties

Here some properties of magnetic flux that scientists and engineers use when trying to explain, design, improve the operation of electrical equipment. There are 7 and they are:

  1. Flux passes through all materials, can’t be insulated.
  2. Lines of force are closed loops passing through the magnet and the space around it.
  3. These loops tend to increase in size as they radiate away from the magnet.
  4. The lines of force have a distinct direction – come from the north, enter the south.
  5. The lines of force never cross each other.
  6. The biggest concentration of lines of force is at the poles and is build maximum field strength there.
  7. Flux lines in large quantities are easy to establish in magnetic materials but non in non-magnetic materials like air.



Law Of Magnets

Of course like all things science and engineering, magnets must follow a law. This is why those subject kick so much bottom, you can figure everything out.

Anyways, the law of magnets is as follows:

When two magnets are brought near each other, the following will happen:

  • like poles will repel.
  • unlike poles will attract.

2 north’s? Repel, try to drive each other away and sometimes one will even flip around to make it attract. This restores the whole natural order and lining up with the magnetic field of the Earth. A north and south? Get your behind over here baby.

Conclusion

Magnets aren’t quite just fun and games kid stuff anymore are they? They are deep, very meaningful and important bits of rock and metal. This opening post on magnets helped lay the foundation for our bigger picture subject of motors. This is why they turn, and take electrical energy and sometimes convert it to mechanical energy to accomplish different forms of work.

You are at the bottom of the page and this is the conclusion. You should now be well versed mainly on the following:

  • Magnetic Materials
  • Magnetic Poles
  • Magnetic Induction
  • Magnetic Fields

Per the youge, if you have any question or comment, use some form on here to contact me. You can leave a comment, shoot me a message.

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