# Low Self-inductance

*Most recent answer: 09/25/2013*

- kevin (age 19)

Canada

You're right that fields can cancel and reduce the self inductance. Think of a coil with a large field inside (per current) threading all the loops in the same way. That makes a big inductance. Now make a second coil around it, wound the opposite way. The fields cancel. So there's very little self-inductance.

I say very little rather than zero. Another way to think of the inductance L is as the coefficient in the expression for the magnetic field energy: LI^{2}/2, where I is the current. The field energy is proportional to the spatial integral of the square of the field. Even for our counter-wound coils there will be little regions with non-zero fields when current flows, so L won't be zero. In fact, even for a straight wire there is a field around the wire so a straight wire has some self-inductance.

Mike W.

*(published on 09/25/2013)*