#### captainkirksdog

##### Member

I've gone brain-dead about some simple algebra. This is the formula for air-core coils:

N^2=L(3a+9b+10c)/0.2a^2

Where:

N=Number of turns

L=inductance in microhenries

a=wire diameter in inches + form diameter

b=length of winding in inches

c=wire diameter in inches

Now I can easily solve for N, but what if I know N and need to solve for L? In other words, I have several unmarked coils that I would like to know the inductance of. Since I don't have an accurate inductance meter, I was hoping to calculate their values. Can someone show me the way to do this? Thanks.