Rotating a smal disk magnet above a large square magnet

[labview1958]

I have rotated a smal disk magnet above a large square magnet while measuring the force between them. For one 360 degree turn, I get a "dc" sine cuve. Why does the force change during rotation? Anyone?

[GAHD]

"dc" sine curve? meaning it goes from force to no force to the same force?

Don't you mean AC(alternating current) where the force goes from positive to nothing to negative?

If the latter it's because the poles of the magnet each are toa different side and youre alligning and disallinging them as you turn it.

If the former and you've got the poles as aligned as you can guess at, my guess would be that one or both have a just ever so slightly tilted magnetic pole from their symmatry point.

Hope that helps, but maby you could explain your experiment a bit more: how are you measuring, what's your exact setup, materials?

[labview1958]

I have placed the large square magnet on the pan of a weighing machine accurate to 0.0001g. The small disc magnet is attached to a actuator/stepper motor and rotated in steps for a full turn(48 steps). The sm all disc magnet is about 2 cm above the centre of the large square magnet. For like poles(repulsion) the amplitude is lower than for unlike poles(attractive).

[GAHD]

check the magnets allignment, it sounds to me like one or both the poles are tilted in relation to the physical plane of the magnets.

[GAHD]

And I'm just verifying: you are shure the magnet attached to the stepper is far enough away not to suffer interfearance from it?

[C1ay]

I have placed the large square magnet on the pan of a weighing machine accurate to 0.0001g. The small disc magnet is attached to a actuator/stepper motor and rotated in steps for a full turn(48 steps). The sm all disc magnet is about 2 cm above the centre of the large square magnet. For like poles(repulsion) the amplitude is lower than for unlike poles(attractive).

How much does the large magnet weigh without the other apparatus nearby? That value is the zero in your force fluctuation, not the zero of the scale.

[labview1958]

The magnets are far away from the stepper. Thus no interference. The large magnet is about 50 grams. The weighing machine can take 200 grams. I am trying to verify whether rotating a magnet such a way should give a constant force or a slightly varying force reading.