Magnet Myths and Misconceptions

[poynt99]

MileHigh
I do indeed agree MH,but you have more than one loop in an electromagnet. Now,what dose the magnetic field look like around two wires close together with the current flowing in the same direction-->see pic below-what shape is the magnetic field MH?.

With only two windings widely-spaced it appears to be peanut shaped.

However, make that 100 closely-spaced windings, over all now what do you have?

Observe above the wire and below the wire, and assume this is the top half of a solenoid coil. Notice that the field above the wire, as a composite, it's direction is to the left. This would be outside the coil. Notice also the field below the wire, as a composite, it's direction is to the right. This would be inside the coil core. Note also that the windings would be much closer together than depicted in your picture, so the field outside and inside would be smoother and more uniform.

The field directions in the pic below are opposite to your pic, but the idea is the same.

[NoBull]

The dips in a coarsely wound solenoid have nothing in common with the undipped field of a magnetic dipole such as a bar magnet.
Decide whether you are analyzing two attracting current loops that far apart or close together (equivalent to a continuous bar magnet) and stop confusing these two cases.
http://youtu.be/Q-V-m_tbbwg
http://youtu.be/-NeF7u_9_Sw?t=1m42s

The B_B field shape extrapolations from one to the other are non sequitir!

The B_B field of a coarse solenoid looks like this:
http://youtu.be/GI2Prj4CGZI

...so OMG!, the field has 4 dips, so all bar magnets must have 4 dips, too...aaaaaaaaaaaa.  (derision intended)

[allcanadian]

@MH

No way, those tests were inconclusive.What you would have to do with a Hall sensor would be to find the actual direction of the magnetic field around the magnet.

I would agree, when considering what I was seeing in real time the individual graphs I posted seemed to lack insight. I mean I understand what I was doing and what I was seeing however it still does not show us the big picture.


As well I had plotted the 2D field on many occasions in the past however every year I clean house. I take literally stacks of notes, thousands of pages of notes and diagrams and burn them in my burning barrel usually with a beer in hand. It is my cleansing, a renewal, to ensure I am not tied to my past thoughts and must look to the future.


In any case, a better option may be using a 3 axis gyro/accelerometer I have on hand and two hall sensors offset by 90 degrees. The hardware setup is simple however the code is going to be a little more difficult to plot all the measures within a three dimensional space. A three dimensional color coded picture of the field would be more meaningful in my opinion.


AC

[NoBull]

Also the B_X magnetic field of a bar magnet mapped with a Hall sensor with Method #1 has a dip in a middle for completely different reason than the dip of the B_B magnetic field between two widely spaced current loops measured with Method #3.

The mere comparison of B_X to B_B is like comparing apples to oranges ...different test subjects notwithstanding.

[poynt99]

OK-one very simple question for all those that think they know all about magnets and magnetism
Why is the north attracted to south but repelled by another north.(and im using north/south as taught in school)-->And dont say the discrete particle theory,as thats absolute crap,and never proven to be fact--just another quantum theory.

Physics dosnt have positive and negative,nor dose it have north and south-->it has CW and CCW.

With electrostatic and magnetic fields there are forces involved. Two positive electrostatic charges will repel one another. Two magnets aligned with opposing poles will repel one another because their fields are of the same "polarity". With magnets, "polarity" really means the over all magnetic moment, vector, or direction of the field.

A ferromagnetic material that has been magnetized has a net electron spin and hence a net magnetic moment. Similar to how two wires carrying current in the same direction will be attracted to each other (due to Lorentz forces), the head of one magnetic moment will be attracted to the tail of another, and so a N attracts a S pole of a PM or solenoid.