Q27. A solenoid of length 0.5 m has a radius of 1 cm and is made up of ' m ' number of turns. It carries a current of 5 A . If the magnitude of the magnetic field inside the solenoid is $6.28 \times 10 ^ { - 3 } \mathrm {~T}$ then the value of $m$ is $\_\_\_\_$ .