(Section 5.15)
Forming a wire into a loop causes the magnetic field to pass through the loop in the same direction. Notice that all sides of the loop, by using the right hand rule, push the magnetic field the same direction. This gives one side of the loop a north pole and the other side a south pole. The magnetic field of the loop is the same of that as a bar magnet.
When a current is run through a cylindrical coil of wire, a solenoid, it
produces a magnetic field like the magnetic field of a bar magnet.