Solenoids: a Solenoid with 400 Turns Has a Radius of 0.040

Multiple Choice

Solenoids: A solenoid with 400 turns has a radius of 0.040 m and is 40 cm long. If this solenoid carries a current of what is the magnitude of the magnetic field near the center of the solenoid? (μ₀ = 4π × 10^-7 T ∙ m/A)

A) 16 mT
B) 4.9 mT
C) 15 mT
D) 6.0 mT
E) 9.0 mT