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.

 

[sardar]

The results of your experiment are interesting and provide valuable data for understanding the behavior of inductors. It is important to note that the reactance of an inductor is dependent on the type of core material used. In the case of an air-core inductor, the reactance is solely due to the inductor's physical structure, and therefore the graph of Vrms vs Irms should pass through the origin. This is because the inductor does not have any additional material that could contribute to the reactance.

However, in the case of an inductor with a soft-iron core, the reactance is not only due to the physical structure of the inductor, but also the magnetic properties of the core material. The soft-iron core has a higher magnetic permeability compared to air, which means it can store more magnetic energy. This results in a higher reactance value for the inductor.

The negative y-intercept on the graph for the soft-iron core inductor indicates that there is a non-zero reactance even when there is no current flowing through the inductor. This is due to the fact that the core material is already storing magnetic energy even without the presence of current. As the current increases, the inductor's reactance also increases, resulting in a non-linear relationship between Vrms and Irms.

In summary, the difference in the core material of the two inductors is the reason why the graph for the soft-iron core inductor cannot pass through the origin. The behavior of inductors is complex and can vary depending on various factors, but your experiment has provided valuable insights into the reactance of inductors. Further investigations and research can help to deepen our understanding of this phenomenon.