- #1

Lomion

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In our lecture, this was the formula given for mutual inductance:

[tex]L_{12} = \frac{N_2}{I_1} \oint_{s_2} B_1 dS_2 [/tex]

According to my own interpretation, this means that the inductance at the second coil due to the first coil (L 1 on 2) is essentially:

The flux caused by [tex]B_1[/tex] from the first coil passing through the area of the second coil. [tex]\Phi_{12} = B_1 A_2[/tex] (assuming B constant to make life simpler). And this flux is linked to the N2 turns of the second coil, and divided by the current from the first coil.

Does this make any sense? My textbook doesn't explain this at all (and in fact, doesn't even have this formula! Argh!) so I used Schaum's outline, but it seems to give me something different.

In example 4 from Schaum's Outline (Ch. 11) in case anyone here has it, it has two concentric coils. First, it calculated the B in the first coil. Then it calculated [tex]\Phi = B_1 A_1[/tex]. (See how it differs from the definition above?)

And then it said [tex]M_{12} = N_2 \frac{\Phi}{I_1}[/tex].

Can someone please clarify why this is? And if I'm using the correct formulas at all?

A better explanation of what exactly is going on with mutual inductance would be appreciated as well!