Motionless Induction

Yes. eg by moving paramagnetic or conductive materials nearby. this is the principle of operation of most automotive ABS sensors.

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Yes; one option is to change current in another nearby coil. Another option (suggested in another post) is to move a piece of ferromagnetic material near the magnet or coil.

According to the acknowledged laws of physics, there is no hope to "generate" anything out of a permanent magnet and a coil without injecting energy in some way.

Francois Grieu

The crankshaft posiition sensor in my old Jeep worked that way. The cps contains a permanent magnet and a coil. It sits very close to the flywheel or flex plate, which has gear teeth. When the engine runs the flex plate spins, and each time a tooth moves past the crank position sensor, the iron in the tooth "grabs" the magnetic field of the permanent magnet and jerks it around (or the magnetic field grabs the gear tooth, same difference). The movement of the magnetic field induces a voltage pulse in the coil, which goes to the car's central computer for controlling the ignition and whatnot.

This is a bit off the subject, but the Jeep cps in particular is prone to wearing out -- over time, heat and vibration cause the little magnet to weaken. Eventually the magnetic field in the cps gets so weak that it simply won't induce enough of a pulse in the coil for the computer to detect. A simple fix is to put a small cap in parallel with the coil. When the cps in my Jeep wore out I found that .01uF got it running properly again.

Jasen Betts wrote:

Electric guitar strings too.

If the coil and magnet remands in a steady state, you can use a near by moving ferrous object that will disturb the reluctance of the field and thus, the static coil will generate a pulse from the field being shifted.

These are known as VRS'es "Variable Reluctance Sensors"

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Thanks for the tip. We fastened a small magnet to the semi flex coupling of our boat's motor. Never hooked it up; but the idea was that using some sort of pickup coil the pulses, as the propeller shaft rotated, rectified, would give some kind of idea on a DC meter or small solid state circuit driving a meter of how fast the prop was turning.

ted text -

Something has to 'change' to cause electric current (from cutting lines of force etc.) to flow. For example if a metal door swung or moved between a magnet and a sensor the magnetic field would change. That change could cause electric current to flow in the sensor coil.