[chewy]

I have a question from school

"What do you think polarized fields mean with the reference to piezoelectric crystal (go on the internet if in doubt)"

Am I on the right track in thinking its the determined + and - ends of the crystal at 90 degrees to the mechanical impact? I have no idea how that would be determined however and what I have found so far relates to the yield emf vs mass of a crystal struck properlly.

Cheers.

 

[backstay]

I have a question from school

"What do you think polarized fields mean with the reference to piezoelectric crystal (go on the internet if in doubt)"

Am I on the right track in thinking its the determined + and - ends of the crystal at 90 degrees to the mechanical impact? I have no idea how that would be determined however and what I have found so far relates to the yield emf vs mass of a crystal struck properlly.

Cheers.

More stuff you will never use in the real world of electrical work.

 

[chewy]

More stuff you will never use in the real world of electrical work.

Nope, dont reckon I will.

 

[triden]

I think they mean that mechanical stress on the crystal will transform it from a non-polar to a polar crystal. It does this by causing a charge separation in the individual atoms of the crystal. When it comes down to it, a separated charge results in an electric field, and therefore an electric potential (emf).

I think that's adequate to answer the question.

All polar means is that the molecule has a separation of electric charge. Piezoelectric crystals are neat because they can automatically align their electron domains in a way that creates a strong field from one face to another. The crystal normal remains non-polar when it is left untouched, but a mechanical stress causes this phenomenon to occur. It's how BBQ sparkers work. I heard these crystals can easily generate over 10,000 volts.

 

[chewy]

I think they mean that mechanical stress on the crystal will transform it from a non-polar to a polar crystal. It does this by causing a charge separation in the individual atoms of the crystal. When it comes down to it, a separated charge results in an electric field, and therefore an electric potential (emf).

I think that's adequate to answer the question.

All polar means is that the molecule has a separation of electric charge. Piezoelectric crystals are neat because they can automatically align their electron domains in a way that creates a strong field from one face to another. The crystal normal remains non-polar when it is left untouched, but a mechanical stress causes this phenomenon to occur. It's how BBQ sparkers work. I heard these crystals can easily generate over 10,000 volts.

Ah I understand it a bit better now after getting the definition of polar thanks. For an example of how many volts is generated we were told between 10 and 30kv.

 

[chewy]

Only a couple of us got the answer and the instructor said he didnt expect anyone to get it, haha.

 

[Safari]

goodwork
he should have given a reward to whoever answers it.then maybe you could share with us in this forum

Sent from my HUAWEI Y210-0100 using Tapatalk 2

 

[Meadow]

Is this for electronics?

I have never heard of an electrician or power engineer needing this.

 

[Big John]

Is this for electronics?

I have never heard of an electrician or power engineer needing this.

They do all kinds of screwball totally inapplicable stuff in apprenticeship classes.

 

[Meadow]

They do all kinds of screwball totally inapplicable stuff in apprenticeship classes.

Looks like it. And people wonder why the trade is going down hill and out over to craigslist. Seriously that has to be the most irrelevant homework questions ever

 

[Going_Commando]

They do all kinds of screwball totally inapplicable stuff in apprenticeship classes.

Yup. I spent many an hour learning stuff with 0 field practicality, but if it helps to apply theory knowledge to it, then I I don't see a downside. Learning how to apply electrical theory to real world applications is how you troubleshoot stuff anyway.

 

[Meadow]

Yup. I spent many an hour learning stuff with 0 field practicality, but if it helps to apply theory knowledge to it, then I I don't see a downside. Learning how to apply electrical theory to real world applications is how you troubleshoot stuff anyway.

A pizo doesn't even help much with electrical theory, something with AC inductance would help a bit more.


IMO, what apprentices should be studying from is Mike Holt material. It is the BEST none BS material you will find if your looking to become an electrician that actually knows what your doing.

 

[Big John]

...But if it helps to apply theory knowledge to it, then I I don't see a downside....

I agree it's important to understand theory, I just think that the focus can be on applicable theory. Electricians do zilch with piezoelectricity and while it's neat to know how stuff works my concern is that you overwhelm apprentices with too much fluff and you run the risk of having them disregard theory that would actually help them in the field because you haven't made a distinction between "interesting" and "useful."

 

[chewy]

Is this for electronics?

I have never heard of an electrician or power engineer needing this.

No, we just did an exam and a homework exam on generating an EMF.

Thermacouple
Magnetic
Chemical
Piezo
Static
Photovoltaic

We had to draw a diagram of each and explain how the emf is generated and then explain a real world application. As an introduction I guess. We are doing LOTO and testing now.

 

[Going_Commando]

I agree it's important to understand theory, I just think that the focus can be on applicable theory. Electricians do zilch with piezoelectricity and while it's neat to know how stuff works my concern is that you overwhelm apprentices with too much fluff and you run the risk of having them disregard theory that would actually help them in the field because you haven't made a distinction between "interesting" and "useful."

The question seemed to be worded such that the student had to apply their electrical theory knowledge to something they know nothing about to see what they could reason out of it. Sure, piezoelectricity is a pointless subject for field sparkies, but reasoning out a problem with what you already know is quite valuable. Plus, there are only so many induction questions that can be asked until they become too easy. Thinking outside the box is never a bad thing.

I might just have a different attitude about it since I got thrown into problems as an apprentice that I had to work out myself, with the theory and very little practical experience I had to work with. My old man couldn't explain his way out of a wet paper bag, so he just threw problems at me, left, and then see what I came up with when he came back later. Most apprentices won't get that kind of experience because in most states it is technically illegal to leave an apprentice unsupervised, so ya gotta attack the situation at a different angle.

 

[Meadow]

No, we just did an exam and a homework exam on generating an EMF.

Thermacouple
Magnetic
Chemical
Piezo
Static
Photovoltaic

We had to draw a diagram of each and explain how the emf is generated and then explain a real world application. As an introduction I guess. We are doing LOTO and testing now.

EMF as in electromagnetic fields or EMF as in electromotive force? The correct term sounds more like how to generate electron flow, but as with most study material wording is something only the creators understand.

Not picking up on you but the wording is off just for beginners.

IMO time would've better spent explaining why pararelled phase sets need to be in the same conduit when its ferromagnetic, something even professional screw up sometimes.

 

[Big John]

The question seemed to be worded such that the student had to apply their electrical theory knowledge to something they know nothing about to see what they could reason out of it. Sure, piezoelectricity is a pointless subject for field sparkies, but reasoning out a problem with what you already know is quite valuable. Plus, there are only so many induction questions that can be asked until they become too easy. Thinking outside the box is never a bad thing....

I get your point, and I don't disagree in theory. But in reality, I don't think apprenticeship courses are well enough taught that they can even begin to approach that caliber of education. So when I see them straying off into that territory, in my experience it's often at the expense of fundamentals, and that frustrates me.

 

[chewy]

EMF as in electromagnetic fields or EMF as in electromotive force? The correct term sounds more like how to generate electron flow, but as with most study material wording is something only the creators understand.

Not picking up on you but the wording is off just for beginners.

IMO time would've better spent explaining why pararelled phase sets need to be in the same conduit when its ferromagnetic, something even professional screw up sometimes.

Electromotive Force is voltage, no? We dont use metallic conduits here unless speced and Ive seen one in 6 years in construction.

 

[Meadow]

Electromotive Force is voltage, no? We dont use metallic conduits here unless speced and Ive seen one in 6 years in construction.

It is voltage, but the abbreviation also stands for electro magnetic fields, which confused me for a second.

 

[Going_Commando]

I get your point, and I don't disagree in theory. But in reality, I don't think apprenticeship courses are well enough taught that they can even begin to approach that caliber of education. So when I see them straying off into that territory, in my experience it's often at the expense of fundamentals, and that frustrates me.

True. Its too bad in most cases instructors follow the old saying of "Those that can't do, teach"