1. The problem statement, all variables and given/known data A 27.0-cm long solenoid 1.25 cm in diameter is to produce a field of 0.215 T at its center. How much current should the solenoid carry if it has 900 turns of the wire? 2. Relevant equations B = μIN / l 3. The attempt at a solution Why am I given the diameter plus the length? Everything else is obvious except this concept. I thought l would equal = 0.27 m. Should I add 0.625 + 0.27 m because the magnetic field is produced at the center?