1) Two solenoids are given- 1st has 1 turn per unit length and 2nd has n turns per unit length.Ratio of magnetic fields at their centres is A) n:1 B) 1:n C) $1:n^{2}$ D) $n^{2}:1$ Answer: Option BExplanation: Magnetic field $\propto$ no. of turns per unit length $\therefore$ Required ratio =1:n
