The mean radius of a toroid is $10 \mathrm{cm}$ and number of turns are $500$. If current flowing through it is $0.1$ ampere. The value of magnetic field (in Tesla) for toroid is ${10}^{-\mathrm{x}}$. Then, the value of $x$ is:-

A long solenoid carrying a current $I$ is placed with its axis vertical as shown in the figure. A particle of mass $m$ and charge $q$ is released from the top of the solenoid. Its acceleration is $(g$ being acceleration due to gravity$)$

What is the magnitude of the torque in $\mathrm{N} \mathrm{m}$ acting on a solenoid which has a magnetic moment of $0.65\mathrm{ }\mathrm{J}\mathrm{ }{\mathrm{T}}^{-1}$ when its axis makes an angle of $30°$ with the direction of the applied uniform horizontal magnetic field of $0.25\mathrm{ }\mathrm{T}$?