Magnets.

[melhookv12]

how strong could a smallish magnet 25mmx25mm be. And is there an efficient way of activating and deactivating it ??

[Gecko1978]

would it not depend on type of magnet. i.e. a simple metal fridge or speaker magnet or an electro magnet.

[Graunching_dave]

melhookv12 said:

how strong could a smallish magnet 25mmx25mm be. And is there an efficient way of activating and deactivating it ??

How do you propose to ‘deactivate’ a non-electo type magnet?

[Gecko1978]

https://www.google.co.uk/url?sa=t&source=web&a...

this might answer your question

[ambuletz]

i'm guessing this is a joke based on a recent magnet thread that already exists.. yawn!

[john2443]

Magnetic chucks are turned on and off, I guess by moving the north/south to cancel each other out.

(You can get electromagnetic ones, but some are mechanical)

[nammynake]

Ask Feynman:

https://www.youtube.com/watch?v=wMFPe-DwULM