A 0.50-m long solenoid consists of 1000 turns of copper wire wound with a 4.0-cm radius. When the current in the solenoid is 18 A, the magnetic field at a point 1.0 cm from the central axis of the solenoid is
a. 0.090 mT.
b. 0.36 mT.
c. 23 mT.
d. 36 mT.
e. 45 mT.
Question 2
Two solenoids are each made of 2000 turns of copper wire per meter. Solenoid I is 2 m long, while solenoid II is 1 m long. When equal currents are present in the two solenoids, the ratio of the magnetic field BI along the axis of solenoid I to the magnetic field BII along the axis of solenoid II, BI/BII, is
a. 1/4.
b. 1/2.
c. 1.
d. 2
e. 4.