Magnet Myths and Misconceptions

[tinman]

As it is for a solenoid coil or bar or cylinder PM magnet magnetized through its legnth.

Below is a pic,and we have a thin pancake coil that can slide from one end of the electromagnet to the other(electromagnet passes through the center of the pancake coil). We are supplying the electromagnet with a DC wave current(like an AC wave,but with a 0 to 6 volt P/P) Where would the maximum voltage(maximum amplitude) be achieved over the 100 ohm resistor- point A,point B or point C.?

[MarkE]

Below is a pic,and we have a thin pancake coil that can slide from one end of the electromagnet to the other(electromagnet passes through the center of the pancake coil). We are supplying the electromagnet with a DC wave current(like an AC wave,but with a 0 to 6 volt P/P) Where would the maximum voltage(maximum amplitude) be achieved over the 100 ohm resistor- point A,point B or point C.?

You have built a transformer.  The coupling coefficient will be highest at the center of the dipole where the magnetic field is nearly perfectly perpendicular to the pick-up coil as opposed to the ends where the field curls substantially.  Depending on the time scale, there could be a big difference between the 0-6V-0 ... voltage waveform and the current waveform.  As to where you will get the maximum reading across a 100 Ohm or any other specific value resistor load depends on among other things the impedance match between that resistor and the reflected impedance back to the power source.  If you want to find out where the field is the strongest, then you need a variable resistor load.  You would then adjust that resistance to find the maximum power point at each location and then compare those power levels to find where the coupling is greatest.

[tinman]

You have built a transformer.  The coupling coefficient will be highest at the center of the dipole where the magnetic field is nearly perfectly perpendicular to the pick-up coil as opposed to the ends where the field curls substantially.  Depending on the time scale, there could be a big difference between the 0-6V-0 ... voltage waveform and the current waveform.  As to where you will get the maximum reading across a 100 Ohm or any other specific value resistor load depends on among other things the impedance match between that resistor and the reflected impedance back to the power source.  If you want to find out where the field is the strongest, then you need a variable resistor load.  You would then adjust that resistance to find the maximum power point at each location and then compare those power levels to find where the coupling is greatest.

Cool
Now please tell me why we generate no power from an inductor if we place the core of that inductor in the center of a magnets dipole on a rotor. So picture a rotor with PM's around it so as the dipole center of the magnets are in the center of the perimeter of the rotor,and we would have what we know as north on the top surface of the rotor,and south on the under side of the rotor.If the magnetic field is nearly perfectly perpendicular to the pick-up coil as you stated,why is no power produced by the inductor/generating coil?.

[tinman]

You have built a transformer. 

Yes,i know i have built a transformer. But this one we can move the secondary along the field produced by the primary.

[poynt99]

Below is a pic,and we have a thin pancake coil that can slide from one end of the electromagnet to the other(electromagnet passes through the center of the pancake coil). We are supplying the electromagnet with a DC wave current(like an AC wave,but with a 0 to 6 volt P/P) Where would the maximum voltage(maximum amplitude) be achieved over the 100 ohm resistor- point A,point B or point C.?

You will obtain the highest voltage reading at point B, but not because of maximal coupling. It comes down to net flux.

At the ends of the coil, positions A and C, the net flux passing through your pickup coil will be significantly lower than what passes through in the middle. The reason being because at the ends, the curling flux has not diverged that much, and most of it will pass through the pickup coil. Therefore, there will be two flux paths (roughly the same net magnitude) passing through the pickup coil, but in opposing directions, largely canceling each other out.

In the middle position point B, the flux density outside the coil is significantly lower (due to the curl) so there will be a higher net flux passing through the pickup coil in this case.

In both cases, all the flux generated within the coil diameter passes through the pickup coil.