Electrets (permanant electric dipoles)

[Mr Skeptic]

I just learned about electrets from wikipedia. Electrets are permanant electric dipoles, essentially the electrical analogue of magnets. My questions, then:

 

1) Why have I never heard of electrets before? Not in college, not in high school, and my physics prof wanted a journal reference before she would believe they exist.

 

2) Do electrets make good toys? If I'm not mistaken, small electrets would allow me to see an electric field, right?

[YT2095]

erm... most of Todays Microphones are Electret, I`m almost Shocked that you (or your prof) have never heard of them!????

[swansont]

I think it may be an engineering term. I don't recall hearing it in physics classes, though certainly the concept of an electric dipole was covered.

[Mr Skeptic]

Oh, I have heard of electric dipoles before, but not any that were macroscopic and permanent. Just things like water molecules and such. The wiki article gives a recipe using waxes, and I never heard of such things. I'll make one if it makes a good toy

[h4tt3n]

Well, I've never heard of them either. Although, I've always wondered what might happen if you froze water while it was under influence of a strong electric field ^^

 

Anyone here have any hands-on experience with these electrets? Will they for instance bend water streaming from a faucet like an electrified comb does?

[John Cuthber]

They are called electrets by analogy with magnets. I'm suprised the prof hadn't heard of them but to be fair, except in microphones, they are pretty obscure.

[Riogho]

Actually, a magnet would techincally be one, since a magnetic field creates an electric one... and so on and so force.

 

You could vibrate a magnet quick enough to cause electric to run through a wire on the other side of the room for instance

[insane_alien]

since a magnetic field creates an electric one

 

ehh that would be a changing magnetic field creates an electric one. static fields don't do squat.

[Riogho]

That is why I mentioned vibrating the magnet

[insane_alien]

yeah, but that you make an alternating field electrets have a static field

[YT2095]

my Alpha radiation detector is electret based also, so it must be reasonably common I expect.

 

[John Cuthber]

Commoner than I thought. I have a similar detector (in need of general maintainance I think) and I didn't know it was electret based. Do you know how it works?

[YT2095]

as far as I know (I`m by Far NOT an expert) the Alpha passes through the aluminised mylar, knocks off electrons underneath in the cavity and that`s then picked up by some sort of detector.

I know the cct employs a HT line also, it`s function I have no idea, perhaps it`s a way to accelerate the particles to give them more clout when they hit the detector???

[Mr Skeptic]

So they're fairly common then. But do they make good toys?