Cd Calculator

heard on the radio but did not catch the details.
any info would be great. looking for simple science projects for kids using stuff around the house

This looks like an urban legend. Modern metal detectors use an oscillator to produce an alternating current flowing through a large multiturn coil in the bottom of the detector. This coil produces a magnetic field causes induced current metal nearby. A second coil detects the magnetic field in the metal near (induction again) is amplified and drives a detection circuit.

If you had an AM radio very crumby 1920s, it would probably tune in the station you listen closely if you have a car but I do not see how you could describe the parts work.

A compass is probably just as well.

As mentioned above, you need an oscillator, a coil, and coil pickups, an amplifier and a speaker. The radio has the speaker of the amplifier circuit, and even the oscillator (in the adjustment mechanism, which is probably a frequency-mixer). I do not know why you need the calculator. The CD case could have an RFID tag which is a kind of antenna coil ... but you still need a wire to a coil issue. And I have no idea of details.