1. An air-core solenoid with 57 turns is 4.96 cm long and has a diameter of 1.46 cm. The permitivity of free space is 4×10−7 T· m/A. How much energy is stored in its magnetic field when it carries a current of 0.634 A ? Answer in units of μJ. 2. B = mu-o (I) (N)/ L Induction= mu-0 (N^2/l) A U= (1/2) Induction (I ^2) 3. First I calculated Induction= 4pie-7 ( 57turns ^2/ .0496m) (pi(.0146^2))= 1.3785e-5 Then I used U = (1/2) induction (0.634 A ^2)= 2.7355μJ I am on the wrong path? I thought of calculating the magentic field as well using my first eqaution= 9.09795 e-4 T but I couldn't find the correct eqaution/ relationship to calculate the energy stored. Thanks in advance for any help!