Magnetic field round current-carrying conductor

Card with copper rod going through middle. Iron filings scattered on card round rod. I pass 8A via an ammeter through rod, but filings scarcely align in the magnetic field at all. (I do tap the card). Can anyone suggest how I could improve the result (e.g. get three separated concentric rings of filings). Thanks
 
Thanks for replies. Yes, the compasses are better, but not as impressive. I thought my iron filings might be a bit heavy (not fine enough, or a bit damp). I notice that the "demonstrations" on youtube are mostly simulations, so perhaps the experiment doesn't really work so well in practice.
 
We generally use plotting compassess, it doesnt take much current to give them a nice kick, but for iron fillings I have some harboard bases covered with shiny gloss paint. They still need a serious amount of tapping though.
 
Wow, blimey well I guess that's inflation then.

Or..

You could shop around... :D





All doing 4 for £20-ish
(And one is doing 4 for £42!) :surprised:
 

Peter Sigsworth

COMMITTEE
Card with copper rod going through middle. Iron filings scattered on card round rod. I pass 8A via an ammeter through rod, but filings scarcely align in the magnetic field at all. (I do tap the card). Can anyone suggest how I could improve the result (e.g. get three separated concentric rings of filings). Tha
@Strike3 .Ok had a play to see if I can get the iron filings to work.
Using a Unilab13V, 8.5 A, Bench Power Unit (from Philip Harris)

1611047862658.png

Set to 4 volts DC (cuts out any higher) through a bench ammeter and 1 metre of PVC coated wire 0.6mm diameter.

Cut a piece of cardboard 12cm2 and cut a 0.5 cm hole in the middle using a cork borer. Then, to make the filings move easier, I put a sheet of clear OHP acetate sheet of the same size over the card, fed the wire through and sprinkled fine iron filings over the surface to get this:

1611047884188.png

The next trick was to get an old Oral-B electric toothbrush without the brush head switch on the power and touch the side of the card whilst holding it steady. The vibrations sorted the problem and allowed the filings to move as the two images below:

1611047994962.png 1611048008608.png

The black line is a shadow of the green wire.
Not spectacular but the toothbrush works.
 
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@Strike3 .Ok had a play to see if I can get the iron filings to work.
Using a Unilab13V, 8.5 A, Bench Power Unit (from Philip Harris)

View attachment 5528

Set to 4 volts DC (cuts out any higher) through a bench ammeter and 1 metre of PVC coated wire 0.6mm diameter.

Cut a piece of cardboard 12cm2 and cut a 0.5 cm hole in the middle using a cork borer. Then, to make the filings move easier, I put a sheet of clear OHP acetate sheet of the same size over the card, fed the wire through and sprinkled fine iron filings over the surface to get this:

View attachment 5529

The next trick was to get an old Oral-B electric tooth brush without the brush head switch on the power and touch the side of the card whilst holding it steady. The vibrations sorted the problem and allowed the filings to move as the two images below:

View attachment 5530 View attachment 5531

The black line is a shadow of the green wire.
Not spectacular but the tooth brush works.
I like the ingenious use of an electric toothbrush.
 
Yes, following Peter Sigsworth's method I attached a vibration generator to the horizontal plate (I don't have an electric toothbrush!). It worked all right, but it's a bit too "high-tech" for such a simple experiment. Prolonged tapping with a pencil is almost as good.
 
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