how to verify Oersted's experiment by design another experiment?(long...)?

Question

the one tests the relationship btw the distance from a currnt carring wire and the strength of the magnetic firld around it. I tried to use the angle between the arrow of a compass pointing before being affected by the current carrying wire and after. Because the direction of the field arround the wire would be affected by the earth magnetic field so the field appears after the wire is nearby should be the vector of the original magnetic field and the earth magnetic field(?) I have a formula: B=Mo(I/2pr) and I use the earth magnetic field as 4800nT(?) since I live in Edmonton. But I am lost about how to use the angle, vector magnetiv field and earth magnetic field to caculate out the real magnetic field I am looking for...(this is the point of my question...). And after i figure out the real magnetic fields WTR the various redius around the wire I would do a strength of the magnetic field-reversed radius graph, hoping the slope would be close to MoI/2p. m I heading the right direction?

Answer 1

Have you any Magnetometers in the cupboards in the Labs where you are. These were large compasses(100mm diameter) which made such experiments more accurate.

I assume in the last part - that you are reversing the current in your long wire!

Draw a vector diagram to scale.
The constant is the earth's field.
The direction of the compass gives the resultant direction in both experiments.

If you have arranged the magnetic field from the current to be perpendiclar to the earth's field you should be able to draw 2 triangles of force with a right angle in them and measure off the unknown fields (which is the 2nd short side in both cases). Then convert your diagram to trig functions and present both in your report.
Contact me if you are unsure of any of this and I'll give it more consideration.