Electromagnetism

what is electromagnetismSince for some reason I am still in an electrical mood today, let’s keep moving forward with the next step in our learning about motor theory. Yesterday, yes, yesterday, a post went up on the first step of this subject – magnets. Magnets set the foundation for how motors work, the why.

More of the why is coming in this post on electromagnetism. All of this is weird, science fiction stuff but it is also so awesome to know about. These magnetic lines and fields are flowing all around us, emanating from most things. Your phone being held up against your head, yikes.

Pieces of electrical equipment such as motors and generators, transformers and alternators, use magnetic electrical circuits in order to operate. Man somehow figured out that he can control this magnetism with his own hands, he can produce or control the magnetizing force.

We can produce a magnetizing force through an electrical current passing through a magnetic coil, like iron.

At the end, we should all be way more familiar with some basic principles of electromagnetism, how a magnetic field can be created using a coil of wire, and how to determine the direction of a magnetic field.

With that, we are off, rolling like a couple of freight trains. Click the button to keep reading.



What Is Electromagnetism?

What is it exactly? For me in simple terms being a knuckle dragger and all, electromagnetism are the principles that define how electrically charged items must behave. We know of magnetic fields and how to control them. Controlling them and using them for me is electromagnetism.

The almighty Wikipedia defines electromagnetism as:

  • the study of the electromagnetic force which is a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually manifests as electromagnetic fields, such as electric fields, magnetic fields and light. The electromagnetic force is one of the four fundamental interactions in nature.

Flux of a Conductor

current carrying conductor

See the individual strands of copper? Each is a current carrying conductor.

If we were to take an ordinary piece of wire, like you take one of those orange extension cords and cut away the orange layer of insulation. Underneath it, is most likely another layer of insulation, black, or cardboard, wrapped paper. Below that level would be three pieces of wire, each with their own sleeve of insulation.

This is where the copper she be.

If you separated that extension cord down to that level where you could see those standard three wires (that’s why there are 3 prongs on the end btw, 3 wires,) those are current carrying conductors. The wires.

So when you read current carrying conductor, just think anything that can carry current or electricity, a wire, or types of metals like we talked about earlier.

If we apply an electrical current to a piece of wire, it would exhibit magnetic characteristics. If we did have a wire carrying electricity, it would act like a magnet and attract certain things, like iron filings. You could drag the wire around and the iron would follow. Makes sense right?

And remember magnets, the lines radiate outward from the poles.

If we took our current carrying conductor, the wire, and placed the bare copper strand vertically let’s say. and then passed it through a piece of paper with iron filings on it, the iron would now form into a shape that physically shows us the presence of a magnetic field.

The direction of the magnetic flux depends on the direction of the flow of current. The cool thing is, we get to control that. We can wire it how we want it to act, you follow me?

So, we can establish a magnetic field in either direction simply by controlling the direction of flow of current in our conductor.

Left Hand Rule for Conductor Flux

left hand rule for conductor flux

You don’t really need to grab it.

Engineers have a cool little rule for determining the direction of conductor flux using what’s called the Left Hand Rule.

If you want to figure out the direction of conductor flux, take your left hand and imagine you were holding the conductor the same way you’d grab the handle of a golf club – with your thumb aligned in the direction that the electrons move through.

The way your fingers wrap around the conductor is the direction of the flux.

Check out the diagram of this bar magnet below.

flux direction in a bar magnet

The direction of flux in a bar magnet.



It shows us the direction that the lines of force take with a bar magnet.

A current carrying conductor which is straight like a wire has no poles. If we shaped the same wire into a loop, bingo bango, it now assumes polar characteristics of a magnet. If we keep making loops over and over again, what are we making now? A coil.

Now compare the diagram below of the magnetic field produced by our coil with the one above of a bar magnet – pretty similar right?

magnetic polarity of a coil

If we were to loop a piece of wire, it shows the same properties as a bar magnet.

Look at how it shows the conductor flux coming out of the left side. This would then be the north pole ho ho ho. Did it really take me that long to make that joke? Dang. Then the conductor flux loops around and re-enters at the other end of the coil, the south pole.

Left Hand Rule for Coils
left hand coil rule

Left Hand Coil Rule.

We can determine the magnetic polarity of a coil in nearly the same way. But different. To do this we use the left hand rule for coils.

This time take the fingers of your left hand and place them in the direction of current flow as it moves through the coiled wire. Your thumb points to the north pole of the device.

Magnetic Strength

At least 3 things impact the magnetic strength of a coil. Yep, any coil. One you make by wrapping a copper wire as much as you can.

They are:

  • number of loops or turns in the coil.
  • amount of current in the coil.
  • type of core material used.

Sometimes materials will be inserted into a coil which can increase the magnetic strength of the coil. These materials are called cores. With a specific core material, magnetic strength will vary with current and the number of turns.

In a coil with a constant number of turns wrapped around a core, current is the only thing that can then impact magnetic strength. More current, stronger. Less current, weaker.




Random Things

Here are a couple of myths, legends, cool facts about magnetism. In fact, I really don’t even know if they are true. I will look them up here, for your benefit and to trip you out a little. Take them for what you will. Magnetic stuff and its relation to Earth is just plain odd. I probably could have included these in the post yesterday but got lazy. Here they are now.

Dogs

  • This might be kind of a myth but judge for yourself. I had heard it before and actually watched my dog poop to see. He did it sometimes, other times he didn’t. Maybe a few hundred dog ancestors ago they were more in tune with magnetic fields. It’s said that dogs poop in alignment with the magnetic field of the earth if they can. Here is a story I found on that from PBS actually. Hmmm. What do you think?

Certain Birds

  • Scientists wondered how birds could migrate so well. They knew that somehow birds could sense portions of the magnetic field of the earth. For example, they now have found that some pigeons have brain cells that record like flight data about the magnetic field and then store it, like a biological compass. Here’s an article on that. And then there are other birds that use magnetite. Here’s an article from National Geographic on that.

North-South Bed?

  • Here is the last one I had heard. I had heard if you can, to line up your bed in a north to south direction. It doesn’t seem legit after barely reading around online but it probably has to do with some slight Feng Shui stuff and again, the magnetic field of the earth. Here are some people discussing it on a physics forum/exchange.

Conclusion

Okay. That wraps up the second step in motor theory. We went over electromagnetism. There are some basic principles of electromagnetism that you now grasp. Hopefully, I didn’t confuse you more than I confused myself lol and you picked up how to use your hand to determine the direction of a magnetic field. And then lastly, you should now also be able to create a magnetic field out in your garage.

Just promise me one thing, when you do start building magnetic fields, no time travel. Dig? Or take me with you.

Most of this material came straight from the book: Electricity 1 – Devices, Circuits, Materials by Thomas Kubala.

Questions? Comments? Complaints? Didn’t think so. Get back to work slacker.

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