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Electromagnetism Question

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yesterdaysyouth:
faraday's law: the amount of voltage induced in a coil is directly proprotional to the rate of change of the magnetic field with respect to the coil.

lenz's law: when the current through a coil changes, an induced voltage is created as a result of the changing electromagnetic field, and the direction of the induced voltage is such that is always opposes the change in current.

so in theroy you could do it either way.... it's just a matter of application, and power available....

Nathaniel Firethorn:
(a) Current.

(b) "Better" how?


- NF

jamz:
Well, you could start making it really cold.  Our magnets here use liquid helium to stay cold enough to have good field strength.  :p



Love, James

Werewolf:
I don't remember the formula for calculating magnetic field strength (measured in Faradays IIRC) but for a stronger magnetic effect use more turns.

I.E.
Using the same size wire @10 Turns wrapped around the core

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and @30 Turns in the same length

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You will get a stronger field out of the 30 turn magnet.

Upping the voltage will result in a stronger field too but since current is a function of voltage and resistance if you up the voltage too high you'll melt the wire.

You can use a smaller wire to get more turns but smaller wire=higher resistance.

This assumes you use DC. If using AC you now have to consider the inductive resistance that exists in the coil and that is a function of turns and frequency IIRC.

Fun little experiment to do though.

P95Carry:
As an engineer I am afraid to say I have forgotten much - books would have to come out.

IIRC tho - large dia wire windings and very high current is way to go.  The volts are just the ''push'' (pressure)  - the current is quantity (volume flow).

I am thinking Coulombs and ''Q'' factors but cerebral rust is most inhibiting!  Then we have flux density - the strength and numbers or frequency of lines of field - which would be A/C.  I seem to think that DC will or can produce the strongest force, power factor for power factor.  It is also therefore a polarized field ... north is north - south is south.  A/C being alternating is changing field poles at frequency of supply - tho something tells me the big magnetic ''picker-uppers'' in scrap yards are A/C driven.

Oh my - have to go back to books for this game

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