|MadSci Network: Physics|
Hi, 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, Nauzad
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