1. The problem statement, all variables and given/known data A 121-turn solenoid with a length of 27 cm and radius of 0.6 cm carries a current of 1.1 A. A second coil of 4 turns is wrapped tightly about this solenoid so that it can be considered to have the same radius as the solenoid. Find the change in the magnetic flux through the coil when the current in the solenoid increases to 4.2 A in a period of 1.13 s. The permeability of a vacuum is 4 pi × 10-7 T • m/A Answer in units of T • m2. 2. Relevant equations Magnetic flux = permeability of a vacuum X N2 X A X I / length 3. The attempt at a solution Change in magnetic flux = permeability of a vacuum X 1252 X A X 4.2 / length - permeability of a vacuum X 1252 X A X 1.1 / length I'm confused how many turns this would have. Would it just be 125 turns? I have no idea how to count the inductance of two solenoids together.