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Published on Oct 9, 2014
The "Top Secret" consists of a spinning top with a radially oriented magnetic field and an associated base that houses a conductive coil. When the top spins past the centre of the base, its changing magnetic field induces a current in the coil which momentarily opens the switch to the battery resulting in powering up the electromagnet. The electromagnet then delivers enough torque to the spinning top to allow it to speed up and spin away from the centre. Since the electromagnet is only engaged when the top crosses near the centre of the base, one 9 volt battery can last for over a week of continual use!