MadSci Network: Physics

Re: How does holding a strong magnet to a quartz watch...

Date: Thu Oct 21 02:11:35 2004
Posted By: Nauzad Tantra, Undergraduate, Production/ Industrial engg., D J Sanghvi college of engg.
Area of science: Physics
ID: 1090685137.Ph

Inside every watch or clock is a small round magnet. Coils are placed
around the magnet. The coils are energised in succession such that the
magnet revolves around its axis (very much like a stepper motor, but much
much simpler). The magnet is coupled with a gear which in turn is linked to
other gears which are coupled to the hands of the clock.

When you place an external magnetic field that is stronger than the field
produced by the coil, the magnet in the watch would interact with the
external field and not get affected by the electro-magnetic field generated
by the coils.

This in turn would not allow the magnet to rotate and hence the gears would
not rotate hence causing the watch to stop.

Hope that helps,


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