HELP! I need a variable magnet for film project

Hey Guys, I really hope someone can help me. Long story short; I am a filmmaker and me and some friends have come up with an idea using Ferrofluid and neodymium magnets to make a cool 30 second short film to help my friend out who's starting out as a sound designer.

However I have no idea about magnets but want to make a variable strength magnet (using a rheostat...?) so I can dial the magnetic current up and down remotely, controlling the magnetized liquid.

We have ;
4 Neodymium magnets
Ferro Fluid
Enthusiasm.

That is all.

I've researched this online a lot for 2 days but have found no clear answer apart from maybe building a rheostat around an electro magnet. Are my Earth magnets rendered useless now? Can they replace the battery in the circuit? Surely they'd be stronger than an even a 12V car battery...

I am new to all of this so any help would be greatly appreciated!

Thank you,

Guy

A few comments to start the discussion.

The big problem here is lack of information:
What magnetic field strength is needed to move the ferro fluid?
How do you want the fluid to move?
What electrical/mechanical workshop facilities do you have available.

want to make a variable strength magnet (using a rheostat...?)

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The obvious thing to use is an electromagnet.
This is a coil of wire with a current flowwing through it.
The greater the current, the stronger the magnetic field.
The current can be varied using a rheostat.

Are my Earth magnets rendered useless now?

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Not necessarily useless, but an inappropriate thing to buy up front for a project like this.
It may be possible to reduce the external field strength from the magnets by making a "magnetic shunt", this would be a mechanical device, what form it would take would depend on the shape of the magnet.

Can they replace the battery in the circuit?

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No.

Surely they'd be stronger than an even a 12V car battery

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You are comparing apples and oranges with that statement.

JimB

JimB,

Thank you for replying! And as you can guess by standard of my questions I know very little about what I am dealing with here.

What magnetic field strength is needed to move the ferro fluid?
Ferrofliud reacts to any magnetic field strong enough to reach it, but (of course) the stronger the better from our testing
N42 Neodymium Magnet with a 32.2kg pull is our strongest magnet.

How do you want the fluid to move?
We are open to experimentation here, but so far we get results very similar to tests we researched online. Such as this.
We really like the spike effect and want the spikes to grow and to be able to control the magnetic reactions rather than trying to hold it closer or further away, which is a bit ham fisted.

What electrical/mechanical workshop facilities do you have available?
I have no access to any workshops or machines.

In terms of the electromagnet this has also cropped up in internet searches but I was hoping there'd be a way to incorporate the neodymium magnets as well.

The magnets are; 3 circular shapes and 1 cuboid.

I have considered building something similar to this with adjustable heights as well, so that the magnetic field can be controlled and manipulated but I think you're right. An electro magnet is potentially easier to build?

What would your advise be?

Again, thank you so much again for answering! This is the first time I've been getting back into science since I was 12 which seems like a long time ago!

Thank you,

Guy

A diffrent approach here would be to use permanent magnets and a means to move them.
An r/c servo might do that trick, you can drive an r/c servo without the radio gear with a r/c servo tester, a fairly simple device.