# Alternation of Magnet Poles in DC and AC Generators

I want to create a generator. The current design I am looking at has several magnets along a wheel, with coils around the outside of the wheel. The wheel then spins generating current.

I know that if I alternate the poles of the magnets, I will be generating AC Current.

So my question is, If instead of alternating the poles of the magnets, If I have all the same poles facing out, while I then be generating DC pulses instead of AC?

First, there is no such thing as a DC "pulse". DC means a steady level, which a pulse by definition is not.

No, you always get AC out of a coil. The coil is driven by changing magnetic field. You can shove a bar magnet down a coil, but it won't produce any steady power. There will be a blip as the magnet moves into the coil, but this is because the magnetic field is changing at that time.

Your generator with all the magnets the same will make AC, but at twice the frequency and less power than if they were alternating. The magnetic field will still change because it will be strong right at a magnet and weaker between them. The magnetic field therefore goes thru one repeating pattern every magnet. Since it's the change in magnetic field that matters, the output won't be as strong since the field goes from peak to 0 (at best) over one cycle.

With the magnets alternating, the field the coil sees will go from positive peak to negative peak repeating every two magnets. That's why the output will be half the frequency but stronger since the magnetic field the coil sees will have stronger variation.

• Thanks so much! I am still slightly confused I think. If all the magnets have the same pole facing out, wouldn't current only be generated in one direction? Or would you be generating current in one direction as the magnet approaches the coil and current in the other direction as the magnet moves away from the coil? – wfbarksdale Jan 5 '12 at 17:02
• @weezy: Yes, the latter, like I said in my answer. – Olin Lathrop Jan 5 '12 at 17:11

that's a very good question. It is actually what I m experimenting these days with.If the poles of the magnets are NOT alternating that is N S N S...and so on then what you get from the coils is a pulsing DC. You do not need rectifier diodes to convert the generated voltage to DC, with their inherent voltage drop of course...the only thing you need to get pure DC is an electrolytic capacitor.