A long solenoid of 50 cm length having100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is: 

${\mathrm{\mu }}_0=4\mathrm{\pi }\times {10}^{-7}{\mathrm{TmA}}^{-1}$

• A

  $3.14\text{ x }{10}^{-4}\mathrm{T}$

• B

  $6.28\text{ x }{10}^{-5}\mathrm{T}$

• C

  $3.14\text{ x }{10}^{-5}\mathrm{T}$

• D

  $6.28\text{ x }{10}^{-4}\mathrm{T}$