1. A long straight wire carries a current of 5.0 A. Find the magnitude of the magnetic field at a distance of 10.0 cm from the center of this wire. 2. A loop of wire has a radius of 20.0 cm. Find the current in this loop of wire if the magnitude of the magnetic field at the center of the loop is 1.00 iT. 3. The magnitude of the magnetic field in the core of a tightly-wound solenoid is 5.0 iT when the solenoid carries a current of 3.0 A. Find the ratio of the number of turns of the solenoid to its lengt (n).