Magnets- is there an actually PERMANENT magnet?

[Dr.Z]

I have heard a bunch of contravirsy about this, but is there truly a permanent magnet?

[Mordred]

Technically no. Permanent magnets can demagnetize via temperature, impacts or being realigned in some fashion. For example an external magnetic field can demagnetize a permanent magnet

[DrP]

I guess it depends on your interpretation of the word permanent. If unaffected by external fields, impacts or temperature changes I thought they were permanent, but could be shown to be wrong.

 

Its like motion... all motion is permanent due to a body's inertia. It will only come to rest if acted upon by an external force. Does this mean that motion in a body is permanent? (sorry if this analogy isn't great - I liked it as a way to get thinking about something that is permanent that can be stopped by external influence).

[Sriman Dutta]

Actually permanent magnets are impossible. Magnets may demagnetise due to pressure, external magnetic fields, application of AC at its ends or due to chaotic alignment of the molecules of the magnet over time. In all cases, the ultimate consequence is that the magnet will lose its magnetic properties.

[DrP]

We still define magnets that can hold that alignment permanent magnets. As I said - it is semantics... is anything permanent at all if you consider the timescales of the universe?

[Mordred]

proton lifetime? its longer than the age of the universe lol.

[Externet]

I think we are all standing on top of a huge one, and its core temperature has been hot for many million years, and still works.

[Sandraa]

Permanent magnet is a name relatively soft magnet. Actually permanent magnets are not permanent. A Permanent Magnet is a material which has ability to resist demagnetization, including filed demagnetization and thermal demagnetization. The ability is characterized by a physical parameter called coercivity.

Edited August 30, 2019 by swansont
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[Silent]

On 9/28/2016 at 9:43 PM, Dr.Z said:

I have heard a bunch of contravirsy about this, but is there truly a permanent magnet?

Nope. Eventually, at some point a magnetized object will demagnetized. Could be 1 year, could be 100,000 years but eventually it will happen.