A long wire is bent into a circular coil of one turn and then into a circular coil of smaller radius having $$\mathrm{n}$$ turns. If the same current passes in both the cases, the ratio of magnetic fields produced at the centre for one turn to that of $$n$$ turns is

A horizontal wire of mass '$$m$$', length '$$l$$' and resistance '$$R$$' is sliding on the vertical rails on which uniform magnetic field '$$B$$' is directed perpendicular. The terminal speed of the wire as it falls under the force of gravity is ( $$\mathrm{g}=$$ acceleration due to gravity)

A straight wire carrying a current (I) is turned into a circular loop. If the magnitude of the magnetic moment associated with it is '$$M$$', then the length of the wire will be

A solenoid of length $$0.4 \mathrm{~m}$$ and having 500 turns of wire carries a current $$3 \mathrm{~A}$$. A thin coil having 10 turns of wire and radius $$0.1 \mathrm{~m}$$ carries current $$0.4 \mathrm{~A}$$. the torque required to hold the coil in the middle of the solenoid with its axis perpendicular to the axis of the solenoid is $$\left(\mu_0=4 \pi \times 10^{-7}\right.$$ SI units, $$\left.\pi^2=10\right)\left(\sin 90^{\circ}=1\right)$$