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# electromagnets to push objects without touching it Answered

hi, i want to make an electromagnetic coil which can push another metal plate without touching it from destance of approx. 50cm .
max voltage allowed is 24 v.please suggest me way of getting electromagnet strong enough to push weight of approx 7kg without touching it.can you also suggest me material that can easily repel electromagnet?please help asap.

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## 10 Replies

KiranS13 (author)2015-09-24

THANKS FOR HELPING

KiranS13 (author)2015-09-11

i'm actually thinking about using dc voltage 24v and around 6A current for this purpose.can you tell me how much weight it can push and from how much distance.

Jack A Lopez (author)2015-09-11

For a DC magnetic field, the rate of change of flux, at any distance from the electromagnet, is zero. So the induced current in the conductor is zero, and the lifing force is zero as well.

Lenz's Law repulsion requires a changing magnetic field, i.e. an AC electromagnet. Or, alternatively, it requires some kind of relative motion between the conductor and magnet which causes the field in the frame of the conductor to change.

rickharris (author)2015-09-11

Very little over a very short distance. you can improve this by making the object magnetic - the stronger the better.

Jack A Lopez (author)2015-09-10

Guessing you want to use magnetic forces to push something up, pushing against that thing's weight, which pushes downwards.

I think the name of this game is called "magnetic levitation",

https://en.wikipedia.org/wiki/Magnetic_levitation

and there's more than one way to do it, e.g. diamagnetism, Meissner effect (for superconductors), induced currents via Lenz's Law, attaching permanent magnets (or electromagnets) to the thing being levitated, ... I dunno. There are a bunch of ways to do this, and the Wiki article linked above mentions several of them.

You say "metal plate" which makes me guess further that you are interested in some kind of setup using induced currents Lenz's Law.

https://en.wikipedia.org/wiki/Electrodynamic_suspe...

I think the trick for that is to choose a metal with both high bulk conductivity, and low mass density (i.e. low weight per unit volume). That ?probably? means aluminum, or some alloy thereof, is going to be your best bet.

By the way, in the demos I have seen for this effect, the levitated conductor tends to get hot, due to the large currents running around in it. So, remember to bring your oven mitts.

;-)

rickharris (author)2015-09-11

Could be an attempt at anti gravity? Back to the future skate board? What ever it is going to need megga current to get 50 cms! But I like optomisim.

rickharris (author)2015-09-10

If you place an aluminium plate close to you electro magnet it will have an induced electrical current in that will create an opposing magnetic field causing the aluminium to be repelled.

the distance may be another thing and you will need a thick bit of aluminium and some experimentation to get it to work.

rickharris (author)2015-09-10

other than that your metal will need to be magnetised.

iceng (author)2015-09-10

800 A for about 8" - - - then I figure 2000 A for 20" not even allowing for that inverse square affect :)

iceng (author)2015-09-10

We don't know your skill set.

Basically you need to induce a circulating current in the metal plate which gives it a magnetic field. Then you create an opposing field to repel the the plate magnet.

However there is an inverse square relationship between your coil and that plate 20 inches away. The energy needed induce over that distance is enormous