Tim said:
Volts have nothing to do with magnetic fields- okay, you can't have current
without voltage,
For a practical electromagnet running at maximum limits, the magnetic
field strength is set by the core material and core shape, and by the
wattage thermal dissipation, and by the grams of copper in the coil
winding ...*not* by the current.
If you try to increase the current, you'll exceed the maximum wattage
unless you replace your coil with one which has fewer turns of thicker
wire, and runs at lower voltage and higher amps. But with fewer
turns, the total amp*turns remains the same as before! So any
attempt to increase only the current is useless.
To make a stronger field, you can add a core, or change its shape.
Or you can crank up the wattage after installing a heat sink. Or
you can add more copper to the coil (replacing the coil with thicker
wire of the same no. of turns, or just adding more turns of the
same gauge already there.) Then change the drive voltage to
get back to max wattage.
Example: the number of turns are irrelevant because if max wattage
is fixed at 10 watts, then 1 amp and 10 volts needs 10 ohms of wire,
which might require 100 turns of thin wire. Or 100 amps at 0.1 volt
would require one single turn of very thick wire to maintain 10 watts
max. Amp-turns is 100 in both cases, so changing the number of
turns can only re-program the volts-amps ratio of the power supply.
It doesn't get you a stronger field.
All this just means that bigger, heavier electromagnets give stronger
fields. And water-cooled electromagnets give stronger fields. But
we already knew that.
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William J. Beaty Research Engineer
[email protected] UW Chem Dept, Bagley Hall RM74
[email protected] Box 351700, Seattle, WA 98195-1700
ph425-222-5066 http//staff.washington.edu/wbeaty/