Helmholtz coils and a Hall Effect probe

[Andrea]

hello,

here is my second message.(and my English is still very bad)
I don't understand these 3 little experiments(we need Helmholtz coils and a Hall Effect probe)

I know I have to draw a graph for each situation but I can't interpret the difference between the theory and the experiment.

1)Measure the magnetic field in the middle of a circular coil crossed by a current I(I max=3 A)
2)Draw a graph to explain the intensity of the magnetic field made by the two cicular coils (radius=a),on the axis of this assembly and for different distances L between the coils.Try to find experimentally the Helmholtz condition(2 b=a) when the field has a maximal homogenity.
3)Using some more little currents (2.A),measure the magnetic field at the end of a solenoid (square coil 500 spires) with an iron bar (the framework of the processing).How is the magnetic changed
-with or without the iron "nucleus"
-if we take the half-number of spires


I have sent 3 images concerning the 2nd question:
1°:2b=4
2°:2 b=8
3°:2b=16

Can you tell me how to comment on those graphs because I must find the Helmholtz curve.
For the 3 experiments,what is the theoretical aspect?(cause I obtain some strange graphs...).I don't know if I have to use some formula's too.

Thank you for your help!

 

[kuruman]

It looks like you did this experiment without understanding the theory behind it, namely what the Helhholtz configuration of coils is and what it is supposed to accomplish. You also don't explain what your 3 sets of measurements 2b = 4, 2b = 8 and 2b = 16 mean. Without a number for the radius a of the coils these are quantitatively meaningless because the important parameter here is the ratio of the distance between coils to the radius. Also your graphs are not labeled, which is a no-no for plots. It looks like in the first two graphs your coils were too close together and in the third one too far apart to satisfy the Helmholtz coil conduction. If you don't know what you are looking for, you will not be able to find it even when you see it.