1.) An 21-turn circular coil of radius 19.7 cm carries a current of 2.49 A. What is the strength of the magnetic field at a point on the coil\'s axis that is 41.1 cm from the center of the coil?
2.) A current of 7.03 A in a solenoid of length 10.8 cm creates a 0.313-T magnetic field at the center of the solenoid. How many turns does this solenoid contain?
3.) A doubly ionized molecule (i.e., a molecule lacking two electrons), moving in a magnetic field, experiences a magnetic force of 5.53 x 10-16 N as it moves at 309 m/s at 79.5° to the direction of the field. Find the magnitude of the magnetic field.