Question

A solenoid of length 50 cm and a radius of cross-section 1 cm has 1000 turns of wire wound over it. If the current carried is 5 A, the magnetic field on its axis, near the centre of the solenoid is approximately (permeability of free space ${{\mu }_{0}}~=4\pi \times {{10}^{-7}}T-m/A$ )

• A. $0.63\times {{10}^{-2}}T$
• B. $1.26\times {{10}^{-2}}T$
• C. $2.51\times {{10}^{-2}}T$
• D. 6.3 T

Answer 1

Answer: (B)

$1.26\times {{10}^{-2}}T$

Answer 2

The magnetic field is given by $B={{\mu }_{0}}ni$ where ${{\mu }_{0}}=4\pi \times {{10}^{-7}}T\,m{{A}^{-1}},$ $n=\frac{1000}{50\times {{10}^{-2}}},i=5A$ $\therefore$ $B=4\pi ={{10}^{-7}}\times \frac{1000}{50\times {{10}^{-2}}}\times 5$ $B=1.26\times {{10}^{-2}}T$