About the experiment to find the reactance of inductor

[lindacheung66]

I have just done an experiment on finding the reactance of (a)an air-core inductor and (b)an inductor with a soft-iron core.
I have plotted a graph of Vrms against Irms for each experiment.
For the graph in (a), the straight line can pass through origin; yet, for the graph in (b), the straight line cannot pass through the origin, but have a negative y-intercept.
However, I cannot find an answer to explain this.
Could anyone please kindly tell me why the graph in (b) cannot pass through the origin??

 

[xts]

It seems to be quite strange result. Have you analysed errors? What is a χ² of the fit you made and what would be χ² for a proportional fit (going through 0,0)?
Or maybe you went out of the linear region of permeability? What was the max current you measured and how many turns your coil has?Post your plots if you want more detailed comments.

 

[lindacheung66]

Since this experiment will be counted in the public exam, I cannot post it on the internet.
Would you mind if you give me your email address so that I can send you my graphs?

 

[xts]

Would you mind if you give me your email address so that I can send you my graphs?

Sent to you as a private message.