Q 12-04-014NEETNEET 2020Top questionEasy
A long solenoid of $50$ cm length having $100$ turns carries a current of $2.5$ A. The magnetic field at the centre of the solenoid is : ($\mu_0 = 4\pi \times 10^{-7}\ \text{T m A}^{-1}$)
Answer: (A) $6.28 \times 10^{-4}$ T
Turns per unit length: $n = \dfrac{100}{0.5} = 200\ \text{m}^{-1}$.
$$B = \mu_0 nI = 4\pi \times 10^{-7} \times 200 \times 2.5 = 2\pi \times 10^{-4} \approx 6.28 \times 10^{-4}\ \text{T}$$
Solution by Sreeraj P, M.Sc Physics