Physics lab formula question - help please

[lloyd21]

I only notice it now, but you were suppose to measure the field outside one end of the solenoid as you move further and further away. Since the coil is so small I assume that is what you did? The question then arises how one is suppose the measure r, form the end or ...? The formula suggests that at r = 0 one gets an unrealistically large magnetic field? Do you know what the length of the solenoid is?

Sorry for the late response, the solenoid is very small, approximately 2cm

 

[lloyd21]

Sorry for the late response, the solenoid is very small, approximately 2cm

 

[andrevdh]

This is another indicator that the measurements could not be correct.
If you calculate the magnetic field inside of the solenoid with the standard formula
B = mu_o IN/L one gets 0.002 T.
Your measurements outside of the solenoid are larger than this value.
Did the magnet have an iron core? This could explain the larger measurements.

 

[lloyd21]

How did you get the numbers for B*(T) ... I just re did the lab again and got different numbers. this is my graph with the fit...https://attachment.outlook.office.net/owa/ChadNiddery@hotmail.com/service.svc/s/GetFileAttachment?id=AQMkADAwATYwMAItYTJhMy05YjY4LTAwAi0wMAoARgAAA1%2BGrg4JVahNrFK%2BtBRQxHMHABLpo8Xq25xEnBcsyMWzy8YAAAIBDAAAABLpo8Xq25xEnBcsyMWzy8YAAABJcj45AAAAARIAEADCm1IHbFWERrKKATpfIEQP&isImagePreview=True&X-OWA-CANARY=MExmzr-Mc0SI8-cmfdNr6lBhb1Ua_9IYsqRCrXT1KBke2gOlwMc_Hyqk1XEIOO0im2agejgNszg.&token=ab71b942-38cf-4b84-98f8-6722154f1278

 

[lloyd21]

the magnetic field recorded i converted to Tesla from mT, and converted the mm, to m

 

[lloyd21]

My professor said this as well..What you want to do is to compare your fit (Y = Ax^n, with n=-3) to the theoretical relation (B = (u0/2pi)(M/r^3) ) . Comparing the two formulae can tell you what the fitted parameter "A" represents.

 

[andrevdh]

I calculated B* from the given formula - the 1/r³ one.

Yes, so the fitted A parameter should give you the experimental value for u_oM/2pi.

Was the core of the solenoid "empty" (filled with air), or did it have some material in it?

 

[lloyd21]

It doesn't say if it was filled or empty...I'm so frustrated

 

[andrevdh]

Did you see something inside of the core (middle) of the solenoid?
Do not worry it will not influence the processing of your data.
I am just trying to make sense of the results.

 

[lloyd21]

No nothing?...

 

[andrevdh]

So there was "air" inside of the core?
That would mean that u_o is applicable here.

 

[lloyd21]

I don't follow? I'm not understanding what my next step is...

 

[andrevdh]

See my #37 post.
That means you can calculate u_o from the fitted A parameter's value.

 

[lloyd21]

Andre, I think I might have it now. But I need a little more help . This is what I am told. and here are my two new graphs.

You need two separate graphs...one for each side.
With your plot you want to determine u0. What you are doing is assuming u0 is unknown, and then using the data to determine u0. Of course, in reality, the value for u0 is known. Hence, by comparing "your" value for u0 to the known value gives an idea how well your experiment went.
To determine u0 you have B = (u0/2pi)(M/r^3), or rewritten: B = (u0 M/2pi)r^(-3). Another way of writing this would be Y = Ax^(-3), with Y and x being variables. If were to write B = (u0 M/2pi)r^(-3) as Y = Ax^(-3), what value would you ascribe to "A".

I think those look right. Now in your post 37# to find B, I get 12500 which seems off for the magnetic field. So how do I get B now to solve for the experimental Mu? And do I do that with both graphs to get two different experimental values for Mu?