There is a solenoid of length 1 m has a radius of 1 cm and is made up of 1000 turns. It carries a current of 10 A. The magnitude of magnetic field inside the solenoid is

8π × 10-3 T 40π × 10-3 T 4π × 10-3 T 0.4π × 10-3 T

4π × 10-3 T

$ B = \mu_0 nI = 4\pi \times 10^{-7} \times 1000\times 10 = 4\pi \times 10^{-3}T$