1. The problem statement, all variables and given/known data I came across a recent problem that asked me to calculate the flux density at the end of a solenoid. I was given the current 3 A , the number of turns per unit length , 12 cm-1 and the using the permeability of free space as 4π × 10^-7 2. Relevant equations The equation I used for this is B=μnI , where n is the number of turns per unit length ( in per meter) and I current. 3. The attempt at a solution I got 144π × 10^-5, this however was not an option and so I was wondering if there were some other factor I had to account for as it is the end of the coil and not for the midpoint for which the equation is defined.