First, consult the lesson plan here for instructions on running a sample lessson and demo based around the one I ran in the classroom for my PHYS 420 project:
Lesson plan [.pdf] Preparing is easy. Unpack everything, set up the power supply and solenoid, and test that before you start.
- Put the fluid in the dish to start, and have it all ready to go.
- Set the solenoid at the right height over the dish, and maybe make a note of the correct current settings needed to cause the effect.
- If you are using the filings demo, have the right amount of filings ready and a funnel to return the filings to their container.
- Have the bar magnets/other magnets you are going to use for the first part set aside, so that you don't use the wrong ones.
- If you are using compasses to illustrate the field/magnetisation, make sure the needles are all magnetized the right way.
- Have paper towels, a sink, gloves nearby in case things go south, and for cleanup.
Thats it!
- Be very careful where you leave your magnets lying around! Especially strong ones. They like to stick together
and to other things, and the worst case is leaving a magnet sitting near the edge of the ferrofluid dish,
where the fluid will try to flow to the magnet.
- The fluid is very stable and keeps quite well, I stored some in my dish for months
with only seran wrap covering the dish, and it still worked well when I used it again later.
- Also, avoid transfering the fluid too often from dish to bottle/jar/storage, for you lose a lot every time in the residue that the fluid leaves behind.
- Stronger magnets produce more spikes, but these are smaller. Sometimes, weaker magnets look cooler since the spikes,
are easier to see and bigger. Holding a magnet below the dish but not right against it will also produce bigger spikes.
- Do not run the solenoid too long! Naturally, it will heat up. It took a few minutes for it to get hot enough to be a worry for me, so there is no need to rush.
However, don't leave it running and forget!
- How easy is it to make the spikes happen?
Very easy. They as soon as you have the fluid in the dish, they appear right away the moment
you bring a magnet near.
- What does it feel like to touch the spiky ball?
I tried poking the ball when there was a strong
magnet under the dish (wearing gloves of course!). It felt strange - the core of it was really tough while
the outside was softer (the spikes were not solid). It felt like sticking my hand into jelly, but the centre
felt like really tough clay or something. After a while of doing this, the (oil based) fluid might have started
to leak through the tips of my glove - so if you plan on doing this a lot make sure to use good gloves lest you
spend time cleaning the fluid off your skin once more.
- Should I let the students play with it?
I value interactivity, and this stuff is a lot of fun. If your table is sturdier
than mine, and the students promise to be careful (and understand that the fluid stains stuff), I think it is perhaps acceptable to let students carefully
play with a weaker magnet under the dish under supervision. Just make sure to tell them not to hold it by the edge
where the fluid might try to escape! Maybe older/maturer students only.