Beginners Electromagnetism Class

[Linda Brown]

Langley.... You said this ..."Like riding a bike I guess. First you have to understand gyroscopes, that's why so many kiddies fall off."

And I know that you must have been kidding us .... but if perhaps you were not I think I need to explain how I learned to ride a bike. My grandparents lived in a townhouse in Georgetown... the front yard was two levels with a steep grade dividing each section. Neighborhood kids would gather and ride their bikes down that grade and then coast even further. I watched that, thought it was neat... grabbed a bike, climbed on and coasted down the grade just the way that they did. Pretty soon that I picked up on the idea that if I pedalled then I could go farther. Trust me.... the idea of a gyroscope never entered my mind.

So my point here is. Answer the question.... How do you ride a bike? <g> Linda

[Linda Brown]

And while I am on the subject of the KISS method ( Keep It Simple Stupid... one of my Dads most commonly used phrases) forgive me while I talk about horses for a moment.

By now most of you know that horsemanship has been a lifelong passion for me.

This is what is happening to us, I think.... because of our passion for what we are talking about we tend to try to say too much. (Simply because we love all of it dearly.) If someone would come to me and ask... How do I ride a horse? My mind would be flooded with all of the things that I have learned in my life.... " Shoulder in" excercises in the dressage arena... how to rate a horse approaching a triple oxer.... How to check a full charging horse coming up to the first barrel in a barrel race at a rodeo.....you pick it... I would be thinking it....But all of that information is not what is needed.

I learned how to tell someone to ride when I worked as a trail guide at the Catalina Stables. We would get a mass of tourists... most of whom had never even sat on a horse . The object was to get them around a four mile trail in the hills overlooking Avalon... have them enjoy themselves and bring everyone home safely.

And note.... with ten riders to get mounted you only have about 30 seconds to give a riding lesson to each one. So the talk was.... " Keep your heels down in the stirrups... sit up straight in the saddle... these are your reins... they are your brakes... pull back gently until you get to the speed you want and then loosen up... dont jab ... showing them how to neck rein their horse was a quick demonstration....and at the end I would simply say. The object is to stay on top and in the middle. And then I would swing up on my big Shadetree and we would be off......never lost a single one.

Thats what we are doing here folks.... KISS. Linda

[langley]

Langley.... You said this ..."Like riding a bike I guess. First you have to understand gyroscopes, that's why so many kiddies fall off."


So my point here is. Answer the question.... How do you ride a bike? <g> Linda

OK who invented the first bike and why did that person think it would stay upright?

it worked and everyone has COPIED the person ever since. Without thinking about it.

The great bicycle conspiracy:

There are several early but unverifiable claims for the invention of bicycle-like machines.

The earliest comes from an illustration found in a church window in Stoke Poges, installed in the 16th century, showing a naked angel on a bicycle-like device,[1] and from a sketch said to be from 1493 and attributed to Gian Giacomo Caprotti, a pupil of Leonardo da Vinci. Hans-Erhard Lessing recently claimed that this last assertion is a purposeful fraud.[2][3] However, the authenticity of the bicycle sketch is still vigorously maintained by followers of Prof. Augusto Marinoni, a lexicographer and philologist, who was entrusted by the Commissione Vinciana of Rome with the transcription of da Vinci's Codex Atlanticus.[4]

Later, and equally unverifiable, is the contention that Comte de Sivrac developed a célérifère in 1791, demonstrating it at the Palais-Royal in France. The célérifère supposedly had two wheels set on a rigid wooden frame and no steering, directional control being limited to that attainable by leaning.[5] A rider was said to have to sat astride the machine and pushed it along using alternate feet. We now know a two-wheeled célérifère never existed (though there were four-wheelers) and it was a misinterpretation by the well known French journalist Louis Baudry de Saunier in 1891.[6][7]
[ed

The verified machines.
The first verifiable claim for a practically-used bicycle belongs to German Baron Karl von Drais, a civil servant to the Grand Duke of Baden in Germany. Drais invented his Laufmaschine (German for "running machine") of 1817 that was called Draisine (English) or draisienne (French) by the press. Karl von Drais patented this design in 1818 which was the first commercially successful two-wheeled, steerable, human-propelled machine commonly called a velocipede, nick-named hobby-horse or dandy horse.[8] It was initially manufactured in Germany and France. It was constructed almost entirely of wood. Hans-Erhard Lessing found from circumstantial evidence that Drais' interest in finding an alternative to the horse was the starvation and death of horses caused by crop failure in 1816 ("Eighteen Hundred and Froze to Death," following the volcanic eruption of Tambora).[

Wiki.

[htmagic]

You know that I adore and respect all of you guys and I think that you are all brilliant. But you have not met the class standard here. Karen asked a very simple question. Where is the SIMPLE answer? I know that this excercise may seem a pain but it is important for her and for me too and the resulting conversations might just surprise all of you.

This is the challenge.... the very simplest explanation. Linda

Linda,

OK, KISS = Keep It Simple Stupid.

I believe Karen's question was "What was the difference between AC and DC?"

OK, the simple answer is for DC, the polarity stays constant, one red wire (positive) and one black wire (negative). Just like a flashlight battery or the battery in your car.

In AC, the polarity of the wires changes. In the US, the polarity switches 60 times a second or 60 cycles per second (sometimes called 60 Hertz [Hz]). In Europe, it changes 50 cycles a second or 50 Hz.

Simple enough?

[PeeTee]

What is polarity? why is that important?

it's not simple enough yet.

You can't explain AC and DC theory in simple terms except to say that they are completely different ways of using electricity....THAT ALL you say until a basic understanding of physical dynamics of conductors and insulators is well understood

That's my opinion only but then I say this because I learned it the hard way.

Electromagnetic theory is boring enough to learn anyhow, so often the only way to learn is to note the inconsistencies and "strangeness-of-it-all" first. that way you begin to understand why it becomes so interesting to learn in the first place.

Peetee le Trickfox

[htmagic]

Thought I defined polarity as a positive pole and a negative pole.
DC stays constant while AC current alternates or changes.
These are simple enough concepts that most can understand...

Since this is Karen's class, Karen, was it simple enough for you to understand?

[PeeTee]

OK...I have a question then......

When you walk across the dry carpet in your wool socks and touch the door-knob and get a shock....was that AC or DC electricity ?

Anyone?

Peetee le Trickfox

[KarenAnn23]

Magic,

Yes undertood the answer...courious about the static energy Q. Pee Tee just asked...???

Karen

[htmagic]

Magic,

Yes undertood the answer...courious about the static energy Q. Pee Tee just asked...???

Karen

Karen,

Here's a good site that explains static electricity as this:

Static electricity is the imbalance of positive and negative charges.

When you walk across the carpet, you are rubbing (transferring) electrons from one insulator to another (the carpet and your feet). So your body has an imbalance of electrons. When you touch the metal doorknob, the excess charge is transferred from your hand to the knob.

Now, from this site:

The term "static" in this case is deceptive, because it implies "no motion," when in reality it is very common and necessary for charge imbalances to flow.

Now, just prior to touching the knob (where discharge occurs), one surface has is neutral (the doorknob) because it has a balance of positive and negative charges and one surface (your body) has an imbalance of charges.

So my question, Karen, is (if you were paying attention), just prior to discharge, would these charges be considered direct current (DC) or alternating current (AC)? Now if you visit the links and click on them for the above quotes I provided, you should have a good idea of the answer.

So, Karen, what is it, DC or AC? (And if you're unsure, take a guess and we'll give you the answer (and explanation) after you give yours.

[KarenAnn23]

Magic,

or anyone else please give me the day to answer before anyone else..I have a lot going on, But, I would like the opportunitie to try to answer.. Thank You

Karen