Author Options:

Replacement of function generator? Answered

sorry earlier i posted reverse of that...i saw a video on utube a man producing magnetic flux from dc current (conveted to AC with help of dc motor)..how that can be done
What i want to stay is you hava a 9v battery a 5v dc motor and a capacitor ow can u produce magnetic flux?
without doing any  implicit changes i mean disturbing the motors etc etc(internally)


Do you happen to have a link to that Youtube video?

I'm never going to be able to find the one you're talking about searching on words like "magnetic flux", "dc current", "motor", etc.  There are just going to be too many hits.

I am guessing the setup you saw in this video was some kind "rotary convertor", 
a motor driving a generator, or something like that.

Still not totally sure what you're talking, erm typing, about.

Well i can't tell that (link) it is something an idea i got and i don't want it to be stolen.
What i want to stay is you hava a 9v battery a 5v dc motor and a capacitor ow can u produce magnetic flux?
without doing any implicit changes i mean disturbing the motors etc etc(internally)

Erm, yeah.  There are idea-thieves are everywhere!  So I guess you can't be too careful.

Steve is right about current carrying wires producing magnetic flux.
This is the principle that explains how electromagnets work.
For example the magnetic flux inside a coil of wire ,with N turns, is directly proportional to the current (in amperes) flowing in the coil, multiplied by the number of turns.  You can also get an increase in magnetic flux by using a ferromagnetic core, like iron, or laminated iron, or that ferrite stuff.

Also there are two kinds of magnetic flux:  constant (DC) magnetic flux and alternating (AC) magnetic flux, and that works pretty much the way you would expect.  Driving DC current through a coil will give you constant magnetic flux in that coil.  Driving AC current through a coil will give an alternating magnetic flux.

Also the magnetic field near a rotating permanent magnet, is an AC field, with AC magnetic flux.

In regards to your questions about a DC motor, the space surrounding a running DC motor is going to a little of each, both some DC magnetic fields, and some weak AC magnetic fields too. 

The strongest of these magnetic fields will of course be inside the motor.

If you attached a permanent magnet to the shaft of your motor, that could give you some big AC magnetic flux.

Then maybe you could put a pick-up coil near that rotating magnet, and get some AC voltage from it, by way of generator action, a.k.a Faraday's Law:
Then that AC voltage would have a frequency the same as the rate of rotation of the motor, e.g a shaft turning at 60 times per second, would give you AC in the pickup coil with a frequency of 60 Hertz.

My final guess is that you want to use the ability of a capacitor to block to DC signals,
by connecting a capacitor in series with the terminals of a running DC motor.  That way you can get some small amount of AC out of the motor through that capacitor.  This AC would be essentially generated by the rotor coils, as they move past  the permanent magnets of the stator, and also get switched in and out by the commutator.  That's kind of a weird idea, you know.  I haven't tried that one before.

Do you mean a rectifier ?

To convert AC to DC, you don't use a motor. You have to use some diodes. See: http://en.wikipedia.org/wiki/Rectifier

An oscillator, well the electrical kind,
switches on and off, and usually is powered by direct current (DC), and so can be thought of as something that converts DC to AC, not the other way around.

Converting AC to DC is usually done using diodes.  A diode is a kind of rectifier,
a two terminal device that only allows current flow through it one way.

Diodes are small, cheap, and ubiquitous, so a circuit made of 1, or 2, or 4 diodes, and usually some capacitors too, is the usual trick used for converting AC into DC.

Of course there are other ways to build a rectifier, like a synchronous rectifier,
and the way that works is by using switches that are (somehow) carefully timed to the same frequency as the input AC waveform.  So you can basically make a switch open when the AC waveform is the positive part of its cycle, and close one the negative part. Or you could make a switch that does the exact opposite.  Usually the switches in a synchronous rectifier are semiconductors of some kind; e.g. transistors, SCRs, etc.

If the switching is mechanical, then this kind of mechanically-timed switch is usually called a "commutator"
Also the wiki article on Rectifier, mentioned some purely mechanical methods for converting AC to DC, here:

Anyway, I think most of the good stuff is in that article on Rectifier,