180708: much of this prjt has to do with detecting small-ish fields as well and
getting some response from the field(s).
Don't forget that the field near the ground is 100v /meter.
180709: and don't forget 'static cling' and that additives exist to nullify it.
And Thompson discovered the e- with a vacuum chamber holding a horiz capacitor to
which was applied 'several thousand volts'
180410: thinking about making a BIG magnetic field using 2 circular, home-made magnets,
separated by ~ 1 foot. The diameter of the electromagnets should be about 8.84 inches,
giving an area of 1 over 2pi. No magical understanding here; just sounded cool. And
the choice of sizes is a tradeoff between cost, weight, easy of seeing effects on
statically charged (styrofoam) 'particles'.
This kind of magnet arrangement is called a
Helmholtz coil
mag gallery calculated plots of magnetic fields, 1 or more magnets visualizing fields with iron filings contained interesting images plus big excerpt from wikipedia on Magnetic Field. wiki/Inductor effects, equations of changing field or current. There are several magnet-related projects 'below' this project. This project serves as something of a collection point for procedures and terms. The terms, if generally useful, will naturally migrate further to glossary_sci.
name | len | dia | ohms | awg | notes |
---|---|---|---|---|---|
mag1 | _ | _ | 1.1 | 24 | _ |
mag2 | 1 15/16 | 1.25 | 9.66 | 24 | _ |
mag3 | 1.5" | 1.25 | 3.85 | 24 | _ |
Met math teach 'rebecca' at 2/6/16 robotics contest. Son 'Forrest' wants to stop a bullet w/ magnetism. (not a good choice). (deflect would even be tough). But I thought about lending him some magnets to 'play' with. And a video: (told mom he'd need a 'bench supply') 'electro magnets' {show permanent magnet electro magnet, spool, iron-ish core, pumpkin shape, compasses, filings on clear plastic surface above magnet(s), poles of a magnet, 'N' etc how to pick up filings, how to clean up (w/ bagged magnet), magnetizing something, hysteresis, bb's, nuts, Algebraically adding magnetic field strengths, superposition, coordinates. gluing perm mags to surface (hot glue, epoxy), 1/r2 (perpen to (invisible) field) VOM, induction, Faraday motors, solenoids, accelerating and decelerating projectiles. _deflecting_ projectiles. } No word from them. maybe too awkward.
The dims of the wound area was 1 15/16" (0.05m) long and had an OD of 1.5". The ID was approx 3/16". The wound dim in radial direction was (1.5-3/16)/2 = 0.56" A separate winding exercise showed about 72 windings/inch. That's 1"/72 windings = 0.0275" per winding. So how many windings would stack in 1 15/16" x 0.56"? 0.56" / 0.275 = 20 layers tall 1 15/16" / 0.275 = 70 turns in each layer. 20 x 70 = 1400 turns
If windings lay atop one another, they'd _mostly_ lie in the groove of the layer beneath - though they'd have to 'jump' to an adjacent groove to fit their direction of the helical turning. The wireCenter bottom winding to wireCenter above winding should a 60 degree angle. Sin(60) is .866 so the savings over having the wireCenters lie directly above one another would be 1-0.866 = 0.134 but mag2 windings have gaps in places so nTurns is probably lower. I've chosen to multiply by 1.125
1400 * 1.125 = 1575
mag2 { calc'g expected B0 = u0 N I / len_m u0 is 4pi * E-7 or 1.256e-6 N is nTurns // 1575 I is current in Amps = volts (16v)/ resistance (9.66) ohms) len_m is length of coil in meters. 0.05m 12.5 E-7 x 1575 x 1.6amps -------------------------- 0.05 meters coil length = 20 x 12.5 E-7 x 2520 = 250 E-7 x 2520 = 630000. E-7 = 0.063 T // ~1/16 Tesla * 10000 gauss/T = 63 gauss = 126 times SF's field
the following have moved to $pub/glossary_sci.html H field Henry inductance Km,relative magnetic permeability Lenz_Law Lorentz_Force Maxwell_3D paramagnetic e0, electric constant Q_factor rcTimeConstant relativitycalculator solenoid weber
1 ft == 0.3048m; 3.28 ft == 1 m 24awg copper. 0.0842 ohms/meter I expected this to be 24 wire diameters per inch but I get 72 turns/inch. Only curious so I can predict the needs of an electromagnet under design. POSSIBILITIES - the 'inch' isn't the length that matters. "centimeters" - it was spec'd as having a thicker covering and magnet wire has just the enamel.