65. In the magnetic material of the rod length l = 50 cm in one layer wound wire so that per centimeter length of the rod 20 turns necessary. Determine the energy W of the magnetic field inside the solenoid, if the current I in the coil is 0.5 A. The area of S-section of the rod is equal to 2 cm 2.

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)