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# Self Inductance

"A fact is a simple statement that everyone believes. It is innocent, unless found guilty. A hypothesis is a novel suggestion that no one wants to believe. It is guilty, until found effective"
Edward Teller

- Consider now a single coil/circuit/loop with N turns. As the current in the loop changes the magnetic field and hence the magnetic flux through the loop changes. This changing "self flux" through Faraday's Law leads to and induced emf in the circuit,

- In the same manner as mutual inductance we define the self inductance of the circuit, L, as follows

> so that the induced emf - sometimes called a "back emf" - is given by
> This "back emf" always opposes the primary emf (due to Lenz's Law), as shown in the diagram at right.

From above, which can be compared to the similar equation for capacitance .

- Calculating self inductance proceeds by the same steps as mutual inductance - Calculate B, calculate magnetic flux, then use the second equation above to determine L.

This girl said she recognized me from the vegetarian club, but I'd never met herbivore.

Dr. C. L. Davis
Physics Department
University of Louisville
email: c.l.davis@louisville.edu