A 0.5 m long solenoid has 400 turns and carries a current of 3 A. Given the permeability of free space μ0 = 4π × 10-7 T·m/A, what is the approximate magnetic field at the center of the solenoid?

Consider two wire arrangements carrying equal current I: Arrangement 1 consists of a semi-circular arc of radius R and two straight infinite wire segments extending along its tangent. Arrangement 2 consists of a semi-circular arc of radius R with two radial straight wires extending to infinity. The ratio of the magnetic field at the center of the semi-circular part in Arrangement 1 to that in Arrangement 2 is:

The magnetic field produced inside a long current-carrying solenoid is: