A closely wound solenoid 80 cm long has 5 layers of windings of 400 turns each. The diameter of the solenoid is 1.8 cm. If the current carried is 8.0 A, estimate the magnitude of B inside the solenoid near its centre.
Length of solenoid L=80cm=0.8m Diameter of solenoid d=1.8cm As d<<L, thus we can treat the solenoid as solenoid of infinite length w.r.t its diameter. Current flowing through the solenoid I=8.0 A Total number of turns N=5×400=2000 turns Number of turns per unit length n=LN ∴ n=0.82000=2500 Magnetic field at the center of solenoid B=μonI ∴ B=4π×10−7×2500×8.0 We get B=2.5×10−2 T
