ECN Forum Forums General Topics of the Trade General Discussion Area 1st year theory

Theory - to what level is a good reality for 1st year persons?

I would think these people should be given more practical theory examples, and leave the advanced stuff for 2nd, 3rd and 4th year persons.

Basic Circuitry is a must! Understanding how to figure Series, Parallel and Combination Circuits + calculate the results is needed from the start.
Along with this, some rudimentary current flow concepts are necessary. Something which describes DC flows and AC flows - yet remains simple enough to understand by entry level persons.
This will assist with connecting AC equipment to Grounded + Ungrounded Multiwire and Polyphase circuits.

A little crash course on Pythagorian Theorems, so they get a glimpse on how Power Factors + Impedances are figured.

Push details on basic of:
* Transformer connections and sizing,
* Motor connections and circuitry,
* Lighting equipment and circuitry,
* Service equipment and related circuitry,
* Panelboards, Feeders, and related figures,
* General Power-Related loads, figures and circuitry (receptacle circuits, etc.),
* HVAC circuits and figures.

Within these areas, the principles of Code-Compliancy, LCL, Planset layout, and the like may be covered enough to give the entry-level persons the insight they really need for the field.

Good luck with your lesson plans!

It's great that you are seeking input like this, in order to give your students the best lessons!
Definitely keep up the great work!!!

Scott35

Yep, ping-pong balls!

Take a dozen or so ping-pong balls - Put them in a clear plastic tube. (A flouresant bulb guard will work) Cap both ends. Allow the balls to have enough room to roll back and forth inside.

Then describe AC generation:

• Electromagnetism pulling one way - Gently tilt the tube one way. Electrons pulled one way.
• Electromagnetism pulling the other way - Gently tilt the tube the other way. Electrons pulled the other way.
• Demonstrate resistance of a load by giving the tube a gentle squeeze in the middle so the balls slow down as they pass slowly back and forth.
• Demonstrate a short by un-capping one end and send them flying all over the room at high speed.

Yes, I just made this up, but an apt analogy. You could use anything....

Scott you got in there before me....

Anyway, before attempting any "serious" therory, some good visual aids are good for basic understanding of the general concept. Bury people in valence rings and high math, you just might get them lost.


[This message has been edited by e57 (edited 10-10-2006).]

Thanks for all the replies. You have given me a lot to think about.

Hotline.... these are the units I teach as they exist the now. I have to wright all the course work my self.
D9AF 11 40 Hours
D9AG 11 40 Hours
D9AH 11 40 Hours

Reno... thanks for that just tying in that link with my units and compairing the two

mahlere.... appriciate your point it is a fine point getting the ballance between theory and practical just right.

e57.... Ping pong balls I use marbles to show current flow. "Glass tube full of marbles represents a wire full of electrons. Add one marble to one end and one pops out the other end instantously no matter how long the tube is."

Kenny

Scott... sorry mate nearly missed your reply there

I am considering adding a new unit covering, inductor-capacitance, motors, power factors but wonder of their relivance to apprentices at this level.

Thinking back to my apprenticeship I learned all these things but then never used the theory out in the field....

So thinking about it, my real question should be are these subjects relevent to learn in any depth, or should they have an awairness, that can then be further developed in their carrear is they so choose to do so.

Kenny

I'd suggest covering 3-phase power as well. This is a tough nut for a lot of people to wrap their heads around in the field, and is much better suited for the classroom. I honestly don't know why this isn't covered more in school- they don't even teach it to electrical engineers in college outside of specialized elective courses few EEs take. A solid understanding on delta and wye 3-phase power in the classroom and a few exercises drilling 1.73 into their heads will go a VERY long way in the field.

I'd recommend awareness of inductors and capacitors restricted to general understanding of what they do to AC circuits as opposed to mathematical equations (the complex phasor mathematics required for any sort of depth is likely beyond their mathematical background anyhow), but I would recommend some depth on PF and how to translate kW to kVA, and maybe some examples relating this to meter readings they may be taking in the field, as opposed to the typical classroom study that has you calculating PF based on the different parts of the circuit.

[This message has been edited by SteveFehr (edited 10-10-2006).]

[This message has been edited by SteveFehr (edited 10-10-2006).]

[This message has been edited by SteveFehr (edited 10-10-2006).]

I made up a demonstration of motor theory for the middle school that was pretty well received. I had a bunch of small bar magnets with a hole drilled through the center (from a matrix print head). I identified the north and south poles with red/green paint. I strung some on brazing rod in different orientations to show attract and repel.
Then I wound an electromagnet on a steel spool with bi-color LEDs across it at the ends. Hooked up one way the LED on one end was red, the other green corresponding to north/south, swap leads to the coil and it swapped colors. That was next to more magnets on rods that repelled and attracted. The last step was a hand wound St Louis motor (permanent magnet DC motor) It also had the same deal with the LEDS on the rotor, wound on the same spools. The comutator was a chunk of .45 brass cut in half and epoxied to the shaft, brushes were springy brass. When you ran the motor you could see which way the rotor was conducting by the color of the LEDs. It really looked pretty cool when it was running. They set it up as a demo at the regional science fair but I wasn't elgible for a prize