# Home experiment - 'seeing' magnetic lines of force?

• LentilSoup7
In summary, the conversation discusses a potential experiment to visualize magnetic field lines using iron dust and a conductor energized with an alternating current. The plan involves using a vertical conductor, a thin sheet of paper, and a toroidal transformer to drive up to 130 amps of current. However, there are concerns about safety and the need for a continuous DC current instead of an AC current. The conversation also suggests using a permanent magnet and iron filings as an alternative method to observe magnetic field lines.
LentilSoup7
TL;DR Summary
equipment:- iron dust, a paper/card board to sprinkle the dust onto, a current generator, large CSA conductor orientated vertically
Thought of doing this one years ago!

Basically, I want to 'see' the magnetic force lines that surround a conductor when energized (with an alternating current).

I appreciate that what I will see (or at least I am hoping to see) is the pattern formed by the iron dust in response the the field lines being created. My understanding is that 'null' points will appear just like with a bar magnet- and I believe the interval/density of these null points (vs iron fillings) will be directly proportional to the amplitude of the AC current. Aka I expected to see smaller gaps between the iron fillings as the conductor current increases.

I know that an alternating current is just that, alternating/reversing- so I do have reservations that the net effect on the iron dust may not be noticable (current frequency will be 50Hz!)- but I am hoping that with a continuous current and thus continuous magnetic density that the iron will arrange itself accordingly. I guess I'll find out. [If not then I could try a Lead-acid battery to pass a DC current and then switch on and off the create and collapse the magnetic field!]

The plan is to arrange a vertical conductor that passes through the centre of a cardboard square, on top of the cardboard I will lay a thin sheet of paper, on the paper I will sprinkle the iron dust. As I apply a (small) voltage to the conductor a current will 'flow' and the magnetic field will excite the dust. The paper may need tapping for the iron to shift.

I will use a toroidal transformer controlled by a variac on the primary side and looping several turns of 25mm² copper conductor in order to drive up to approx. 130 Amps (at mV only). Hopefully this creates enough magnetic flux density T to excite and move the iron dust!

If anyone has performed this experiment (or similar) before or has any thoughts/suggestions on this then please let me know.

If I get some results as anticipated then I will follow up with observed results.

Stay safe - experiment at home :)

LentilSoup7

It is good that you're curious. But there are ways to do experiments without the risk of injury.

First, AC current reverses the magnetic field each cycle. You need a DC current.

130 amps DC current is too much to do safely.

Why not use a permanent magnet and iron filings? That shows the same field lines that an electromagnet would. There is nothing additional you could learn about field lined using an electromagnet.

Are you working at home alone, or in a laboratory working with other people and a supervisor?

berkeman
Welcome to the PF.
LentilSoup7 said:
Summary:: equipment:- iron dust, a paper/card board to sprinkle the dust onto, a current generator, large CSA conductor orientated vertically

in order to drive up to approx. 130 Amps
You don't need 130A to see these effects. This YouTube video uses about 5A at a couple of volts to get some great effects. Stick with small C-D size batteries for much safer experiments until you learn a lot more about electrical and battery safety, please. And stay curious!

davenn and anorlunda
Take one school definition of a magnetic line of force: "The path that an isolated North Pole would take"

I have done the following demo and it is really impressive for such a simple setup.
Take a plastic bucket full of water.
Take a bar magnet and clamp it horizontally on the water surface in the middle.
Take another long magnetised steel rod (stroking method works well) floating vertically through a cork at its N end. The N end acts just like an isolated pole. The S end is affected by the bar magnet but gravity keeps the rod almost vertical.

It will leave the N of the bar magnet and slowly follow the classic curve shape of the field lines round a bar magnet, arriving at the S end. It floats 'away from' the N end (North North East direction) to start with and moves as if by magic. I reckon that beats the iron filings demo any day. You can buy strong bar magnets these days so the experiment can easily be done at home. It will impress family and friends at Christmas and you can fool people that Isolated North Poles Exist, too!

256bits, NascentOxygen, berkeman and 1 other person
anorlunda said:
It is good that you're curious. But there are ways to do experiments without the risk of injury.

First, AC current reverses the magnetic field each cycle. You need a DC current.

130 amps DC current is too much to do safely.

Why not use a permanent magnet and iron filings? That shows the same field lines that an electromagnet would. There is nothing additional you could learn about field lined using an electromagnet.

Are you working at home alone, or in a laboratory working with other people and a supervisor?
Hi anorlunda, thanks for the advise and caution.

I am working from home unsupervised however I feel I am competent to perform basic tests and measurements safely. I have various control measures in place that reduce the level of risk to a level I feel acceptable. I understand that safety is paramount when exploring the effects of electricity and I do not take this lightly.

However, if a DC current will be required then I will use a extra low voltage battery of some description!

Many thanks!

berkeman said:
Welcome to the PF.

You don't need 130A to see these effects. This YouTube video uses about 5A at a couple of volts to get some great effects. Stick with small C-D size batteries for much safer experiments until you learn a lot more about electrical and battery safety, please. And stay curious!

Excellent video, that's what I'm after.

berkeman
sophiecentaur said:
Take one school definition of a magnetic line of force: "The path that an isolated North Pole would take"

I have done the following demo and it is really impressive for such a simple setup.
Take a plastic bucket full of water.
Take a bar magnet and clamp it horizontally on the water surface in the middle.
Take another long magnetised steel rod (stroking method works well) floating vertically through a cork at its N end. The N end acts just like an isolated pole. The S end is affected by the bar magnet but gravity keeps the rod almost vertical.

It will leave the N of the bar magnet and slowly follow the classic curve shape of the field lines round a bar magnet, arriving at the S end. It floats 'away from' the N end (North North East direction) to start with and moves as if by magic. I reckon that beats the iron filings demo any day. You can buy strong bar magnets these days so the experiment can easily be done at home. It will impress family and friends at Christmas and you can fool people that Isolated North Poles Exist, too!
Oh excellent that sounds like a gooden'

Thanks for that, I'll give that ago!

berkeman

## 1. What materials do I need for this experiment?

To see magnetic lines of force, you will need a bar magnet, iron filings, a piece of paper, and a shallow dish or tray.

## 2. How do I set up the experiment?

Place the bar magnet on the piece of paper and sprinkle iron filings around it. Then, gently tap the paper to evenly distribute the filings. Place the paper on the shallow dish or tray to catch any filings that fall off.

## 3. What will I observe during the experiment?

You will see the iron filings aligning themselves along the magnetic lines of force, creating a pattern that resembles the shape of the magnet.

## 4. Can I use any type of magnet for this experiment?

Yes, you can use any type of magnet, but the stronger the magnet, the more visible the magnetic lines of force will be.

## 5. Is this experiment safe to do at home?

Yes, this experiment is safe as long as proper precautions are taken. Keep the magnet away from electronic devices, and make sure to clean up any spilled iron filings to avoid ingestion.

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